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No 3G icon or data connection

Hello everyone,
I got my Captivate yesterday shipped from letstalk.com. Everything with it has been working well, except I don't get a data connection with it at all, except WiFi.
As instructed by the sticker on the box the sim I am using is from my old phone, a Samsung SGH-A707 flip phone. The sim is a little over two years old. When the sim is in that phone, I get a 3G icon immediately.
I have tried turning the phone off, leaving it for several minutes, turning it back on again. Also removing the battery.
When I go to Settings, Wireless and Networks, Mobile Networks, Access Point Names, I see ATT WAP listed. I have tried adding another Access Point Network based on settings seen elsewhere in this forum which differed slightly by specifying a username and password, and not having the proxy and port set. But selecting this other APN has no change.
When I go to Network Operators all I see is an unselectable 'Default Setup' item. Others have reported seeing network connection information there, can anyone confirm on their Captivate?
Checking or unchecking 'Data roaming' does not seem to have any effect.
Under Settings, About Phone, Status the Mobile Network Type is listed as 'HSDPA' but Mobile Network State is 'Disconnected'.
LetsTalk are sending me a new SIM to try, but since I get a 3G connection on my old phone my suspicion is that this is a phone problem.
Does anyone have any other ideas though? Any help would be much appreciated.

Wow well you found something I hadn't yet. There was some talk about whether the captivate did hsdpa or not.. and according to the setting you looked at, it does. In that setting does it show your network is on aT&T? You shouldn't have to create a new APN, the default one should work. Sure you don't have the phone in airplane mode? I'm sure that's a stupid question, just asking.

If you don't have a 3G sim card I hear 3G wont work. You can get a new sim from ATT for free. Oh and about hsdpa ATT disables that Icon and uses a 3G one. I seen a test somewhere with two dif phones one with a 3G icon and one with the H getting the same speeds.

radi0chik said:
Wow well you found something I hadn't yet. There was some talk about whether the captivate did hsdpa or not.. and according to the setting you looked at, it does. In that setting does it show your network is on aT&T? You shouldn't have to create a new APN, the default one should work. Sure you don't have the phone in airplane mode? I'm sure that's a stupid question, just asking.
Click to expand...
Click to collapse
Yeah it shows AT&T under Network.
Nope, not in airplane mode, but thanks for checking, I'd rather you'd assume I was stupid than not ask me the question!
YellowGTO said:
If you don't have a 3G sim card I hear 3G wont work. You can get a new sim from ATT for free. Oh and about hsdpa ATT disables that Icon and uses a 3G one. I seen a test somewhere with two dif phones one with a 3G icon and one with the H getting the same speeds.
Click to expand...
Click to collapse
It is a 3G sim, at least that's what it is labeled as. Like I said I (apparently) got a 3G signal on my old phone. And a new sim is on the way.

on the sim does it say 3G with flames around it lol (thats how my last sim was and it was 3G)

I went to the ATT store to get my captivate. I had an old sim ATT logo with flames that worked in a N1, N97, Bold 9700 and iPhone. I too showed no 3G. They had to replace my sim and it started working. They couldn't explain it.
-JChao

labbu63 said:
on the sim does it say 3G with flames around it lol (thats how my last sim was and it was 3G)
Click to expand...
Click to collapse
That's the one, flames and 3G.
jiayi345 said:
I went to the ATT store to get my captivate. I had an old sim ATT logo with flames that worked in a N1, N97, Bold 9700 and iPhone. I too showed no 3G. They had to replace my sim and it started working. They couldn't explain it.
-JChao
Click to expand...
Click to collapse
Great, that gives me some hope the new sim that is on the way could fix it, thanks!

I had this problem as well. This fix worked for me:
Settings > Wireless and network > Mobile Networks
Check both boxes
- Use packet data
- Data roaming
ATT / Captivate Android 2.2
Hope this helps,

Did you find a solution for this? I'm having the exact same problem with my Captivate. No 3G icon and no packet data connection or mms. When I try to go to a page it immediately gives me the "not found: check your data connection" page, and when I try to send a mms, the 3G icon appears like if it was trying to connect and send it and then disappears when the message fails to send.

I just updated to 2.2 today and I no longer have 3G as well.

just an FYI as long as wifi is turned on you will not see the 3g icon.
I have noticed that when you turn wifi off you generally will not see the 3g icon until you do something with the phone that requires data connections
Turn off wifi and try opening a website via browser...the 3G icon should pop-up automatically at that point

scottlinux said:
I had this problem as well. This fix worked for me:
Settings > Wireless and network > Mobile Networks
Check both boxes
- Use packet data
- Data roaming
ATT / Captivate Android 2.2
Hope this helps,
Click to expand...
Click to collapse
Hello sir, I tried this and now i have 3G(icon popped up and internet/mms works) but am i incurring roaming charges?

For me even that's not working, I think my stupid phone is broken.

When I got a refub'ed Captivate for my partner via AT&T online store since it was only $49, I followed the instructions that came on the box, and everything worked except no 3G/data. So thinking that it might be because of a refurb'ed unit, I called AT&T. They told me to bring it into a corp office store. Fortunately, there's one right down the street from me. I took it in, they fiddled with it for about an hour, including swapping 3 different SIMs, and told me that it was a defective phone. I asked then how do I get a replacement. The rep told me to contact cust service for them to ship a replacement out and it'll include instruction to ship the defective one back since they can't replace refurb unit there at the store. So I went out to my car, called the cust service. The cust service rep told me that I have to send the defective one in first before they'll send me a replacement. I got angry and I went right back in the store, grabbed the rep that was helping me out and told him to please talk to the cust service rep to work things out because I'm not leaving the store until it's resolved. So they talked on the phone for about another 30 min. Then they hung up. The rep fiddled with it for another min, then handed me the phone and the 3G/data was working. Appearantly it was the way that the phone was registered with the system, something was out of whack and 3G/data was not available for that phone line. I then recalled that when I ordered the phone from AT&T, I got an email with instructions that I had to follow, which I did, then I followed the instructions that came with the box. I didn't think much at the time, but it seems like the instruction was telling to do the same thing as the email's instruction was except it was via a slightly different way. So I think I might have inadvertly register the phone twice. In any case, when that happens, 3G/data is not available and yet, the reps checking in the system found the account was setup correctly with the proper plans, changed plans, swapped SIMs, and came to the conclusion of defective phone when the phone was perfectly fine. I don't know if this will help any one. But if your phone is not flashed or rooted, you might want to have AT&T check your account and phone registration.

Go to Settings -> Wireless and network -> Mobile networks -> Access Point Names. Inside that option go to Menu -> Reset to default. (Reboot your phone)
Worked for me, i have a samsung captivate thats rooted running on 2.2 froyo and i was deleting some user data,believe it was dialer data (do not delete that, it also deletes your texts) and i all of a sudden my internet stopped working,i tried every setting and i even think there weren't any APN in the list of APNs because of deleting rampage, so i reset my phone and after that i reset the APN back to default settings and rebooted my phone and it worked. For some of you guys, if it still has an APN(the cingular one) in the list of APNs then all you have to do is reset it back to default by clicking menu with the menu button on your phone and click reset. It should work.

Sreenadh said:
Go to Settings -> Wireless and network -> Mobile networks -> Access Point Names. Inside that option go to Menu -> Reset to default. (Reboot your phone)
Worked for me, i have a samsung captivate thats rooted running on 2.2 froyo and i was deleting some user data,believe it was dialer data (do not delete that, it also deletes your texts) and i all of a sudden my internet stopped working,i tried every setting and i even think there weren't any APN in the list of APNs because of deleting rampage, so i reset my phone and after that i reset the APN back to default settings and rebooted my phone and it worked. For some of you guys, if it still has an APN(the cingular one) in the list of APNs then all you have to do is reset it back to default by clicking menu with the menu button on your phone and click reset. It should work.
Click to expand...
Click to collapse
you just replied to a thread 5 months dead..

Thank you for updating.
Sreenadh said:
Go to Settings -> Wireless and network -> Mobile networks -> Access Point Names. Inside that option go to Menu -> Reset to default. (Reboot your phone)
Click to expand...
Click to collapse
Worked like a charm on my Samsung Vibrant S on Virigin ... this gem of a tip shall be remembered. This started yesterday on the road when data was needed for a work emergency. If only I'd known it then. :-(
Now to fix the Wi-fi from turning itself on and off of it's own free will. *sigh*
Thanks for posting on an old post Sreenadh. You saved the day!

TRusselo said:
you just replied to a thread 5 months dead..
Click to expand...
Click to collapse
...and, it looks like someone found it useful.. Five months, or five days, or five minutes.. If it isn't helping, why say anything at all?
roguegrl said:
Worked like a charm on my Samsung Vibrant S on Virigin ... this gem of a tip shall be remembered. This started yesterday on the road when data was needed for a work emergency. If only I'd known it then. :-(
Now to fix the Wi-fi from turning itself on and off of it's own free will. *sigh*
Thanks for posting on an old post Sreenadh. You saved the day!
Click to expand...
Click to collapse

Hey Guys ok so i am with Rogers in Toronto...I flashed it to stock but have flashed it using AT&T stock (Dont ask why) and now i am unable to use my data... Any help would be greatly appreciated...i am able to use my phone with no issues....

Got my 3G back.
Sreenadh said:
Go to Settings -> Wireless and network -> Mobile networks -> Access Point Names. Inside that option go to Menu -> Reset to default. (Reboot your phone)
Worked for me, i have a samsung captivate thats rooted running on 2.2 froyo and i was deleting some user data,believe it was dialer data (do not delete that, it also deletes your texts) and i all of a sudden my internet stopped working,i tried every setting and i even think there weren't any APN in the list of APNs because of deleting rampage, so i reset my phone and after that i reset the APN back to default settings and rebooted my phone and it worked. For some of you guys, if it still has an APN(the cingular one) in the list of APNs then all you have to do is reset it back to default by clicking menu with the menu button on your phone and click reset. It should work.
Click to expand...
Click to collapse
Dude, thank you so much !

[Q] anyone getting sim card does not allow connection to this network?

I have gotten this message 3 times in the last 5 days. Each time I need to do a reboot to restore cellular/sms service (toggling airplane, wifi, bluetooth, sync, and 4g do not restore cellular/sms). The phone has the same AT&T sim card since day 1 and I have never removed it.
Is this a faulty phone, sim card or both?

gtabfish said:
I have gotten this message 3 times in the last 5 days. Each time I need to do a reboot to restore cellular/sms service (toggling airplane, wifi, bluetooth, sync, and 4g do not restore cellular/sms). The phone has the same AT&T sim card since day 1 and I have never removed it.
Is this a faulty phone, sim card or both?
Click to expand...
Click to collapse
Did the sim come with the phone? ATRIX 2 needs newest of sim cards to function properly. If that's not the problem then I'm not to sure.
Sent from my MB865 using XDA App

Yes, same sim card that came with phone.

Could be a faulty Sim, i've had that happen before with other phones, just go to at &t and show them the problem, they should replace it for you!
Sent from my MZ617 using Tapatalk

(Hope you understand my english)
I wasn't able to solve this problem about an year. But did. And totally sure that it is Device's defect (in some cases it is a ROM deffect as in my case, in other - hardware. Smth like stack overflow issues at GSM controller or so). A year ago when I had face this "sim card does not allow connection... " problem, there are no google serch results on this keywords request. Any. To remove this message I was ought to reboot my device every time it appears. And I was thinking that it is normal behaviour for my device. But now there are lot of complainings at the web ( minimum 5 of Galaxy Tabs P1000, thousands of HTC Disire, few motorolla Deffy, 10 Galaxy Ace, few of Nexus S and so on), so I understand that I'm not alone, and problem is known. So I went to Samsungs Service and they confirmed that it is famous problem, have flashed my phone with some magic ROM (magic because it is official but does not available anywhere in the web, XDA or samsung sites! ) and now my phone works fine. Any other solutions like battery removing, *#*#4636#*#* sirvice menu, new sim-card, flashing variety of modems and roms, didn't helps me. This is not faulty sim. This is serious device's defect. Bring your phone to manufacturer and let them repair it or give your money back. This is their problem not your.

using old 3g prior sim card
With ATT---If you took your old 3g sim card out of old phone and used it. You will get this message. You need to activate the 4g card that came with phone

537magspc said:
With ATT---If you took your old 3g sim card out of old phone and used it. You will get this message. You need to activate the 4g card that came with phone
Click to expand...
Click to collapse
Not true.I'm using my old 3g sim with zero issues.
Sent from my MB865 using XDA

Same issue in Mumbai India
CS4 said:
(Hope you understand my english)
I wasn't able to solve this problem about an year. But did. And totally sure that it is Device's defect (in some cases it is a ROM deffect as in my case, in other - hardware. Smth like stack overflow issues at GSM controller or so). A year ago when I had face this "sim card does not allow connection... " problem, there are no google serch results on this keywords request. Any. To remove this message I was ought to reboot my device every time it appears. And I was thinking that it is normal behaviour for my device. But now there are lot of complainings at the web ( minimum 5 of Galaxy Tabs P1000, thousands of HTC Disire, few motorolla Deffy, 10 Galaxy Ace, few of Nexus S and so on), so I understand that I'm not alone, and problem is known. So I went to Samsungs Service and they confirmed that it is famous problem, have flashed my phone with some magic ROM (magic because it is official but does not available anywhere in the web, XDA or samsung sites! ) and now my phone works fine. Any other solutions like battery removing, *#*#4636#*#* sirvice menu, new sim-card, flashing variety of modems and roms, didn't helps me. This is not faulty sim. This is serious device's defect. Bring your phone to manufacturer and let them repair it or give your money back. This is their problem not your.
Click to expand...
Click to collapse
I have exactly the same issue randomly at times when I try to register on network manually (MTNL Dolphin 3G - Mumbai). Unrooted MB865 ver 2.3.6 & updated on 18th May 2012 to System Ver 55.28.37.MB865.AsiaRetail.en03. If I keep the setting as Automatic in Type of Network & Operator it functions fine fluctuating between Dolphin for local access & CellOne on roaming access in the same area based on cell tower connection the phone registers on alternating between "E" & "H" automatically based on cell mast direction proximity, however if I select 3G only and uncheck automatic for operator then the phone searches for signal for a very long time and fails to show any operator saying "no connection available" & sometimes when "Dolphin" network does appear and try to select manually get the error as "this sim card does not allow connection to this network". I did complain with the service provider and they were supposed to get back to me after checking in their switchboard exchange where I also provided them my SIM number in addition to my cellphone number(no response). Also as is case with poor service of all Indian cell network providers even in urban cities, also face random peculiar issue of call not being received inspite of signal available on the phone & network asking me to recheck the number I have dialled while placing outgoing calls though it is ok and signal is sufficient. Also "Network Speed Booster" app looks like a lot of bull (any other good apps??)
I needed to know using the secret Menu *#*#4636#*#* for 3G GSM service which kind of network I should ideally select for best results & does this setting override the regular menu network settings??
I get "G", "E", "H" randomly based on my locations but no "3G" or "H+" and further at times these icons are grey and sometimes blue and in either cases randomly at different locations sometimes data throughput is not there as only one of the arrow shows active blinking. Any advise on the status based on colors and the blinking of the arrows?? Thanks!

[Not-Fixed] How to install new Z3 D6603 LTE on AT&T network

[Not Fixed] see bottom of this post.
It is fairly easy to install a new D6603 to work completly on the AT&T network. It is not so easy to find the answer of how to do it in the threads and posts. I tried many suggestions and wasted a lot of time. Hopefully this will save you from that fate.
First you must know that you can't use the IMEI number of your new phone if you want it to work completly as it should. If you use the Z3 IMEI you will have trouble with data of various sorts and the phone will go off line when on LTE after 20 or 30 minutes and you will not receive calls or SMS messages. I do not know why but it has been suggested that the AT&T network does not recognise this phone so it causes trouble.
If you have an AT&T nano-sim from your old phone then just put it in the phone. (Cut downs work but can cause other problems some say.) When the SIM is inserted for the first time into a new phone there is a prompt that asks if you want to download the APN. Hit 'yes' and the phone downloads the APN itself.
If it does not ask then go to Settings>More>Mobile Networks>Prefered Network Type and be sure LTE (Preferred) is selected. Then connect your phone to the internet and then go to Settings>More>Internet Settings and select AT&T. You should be good to go.
If you need to get a nano-sim then go to the AT&T store or call and they will give you one or send you one for free. You will need to use the IMEI number from a LTE phone that is already on the AT&T system. You can use your old phone or borrow the number from someone. If the rep installs the sim in the Z3 with the 6603 IMEI don't worry. Just call support later and tell them you sent your new phone back and want to go back to your old IMEI or have a new IMEI (from an existing AT&T phone). They will enter it and off you go. The phone from the IMEI will show in the picture on your account page. Big deal!
Update: This worked for hours last night but this morning it is back to not receiving calls. Simply turning wifi off and it began to receive calls as GPRS was switched back on. My wifi was on which has been said to cause problems. I will test with wifi off and report back. Had "no service" instead of AT&T on upper left of lock screen. A full shut down for several minutes than re-boot solved that.

YMMV. I've been on ATT with a Z3 purchased from Sony store for several months and it was registered in an ATT store by scanning the IMEI off the box followed by updating Internet settings in Setup. ATT online shows unknown model but everything works including LTE and MMS. There is something else involved when problems like this occur probably some setting not getting reset. I registered the Z3 on a new line with a new Sim card because I wanted to take my time moving stuff off my old phone--this may have avoided the problems.

JudH said:
YMMV. I've been on ATT with a Z3 purchased from Sony store for several months and it was registered in an ATT store by scanning the IMEI off the box followed by updating Internet settings in Setup. ATT online shows unknown model but everything works including LTE and MMS. There is something else involved when problems like this occur probably some setting not getting reset. I registered the Z3 on a new line with a new Sim card because I wanted to take my time moving stuff off my old phone--this may have avoided the problems.
Click to expand...
Click to collapse
I've also had no problems with my Z3 on AT&T. Works great, receives sms/mms immediately, etc..

esheesle said:
I've also had no problems with my Z3 on AT&T. Works great, receives sms/mms immediately, etc..
Click to expand...
Click to collapse
AT&T's system sometimes takes a while to get updated with new IMEIs that trigger LTE provisioning for a users' account.
Once your account is provisioned for LTE you never have to worry about it again, but sometimes if you have a phone the system doesn't recognize, it is a pain to get AT&T to properly provision your account. Supposedly properly trained in-store reps can do it - the key being "properly trained" - Never try to do anything "unusual" by calling AT&T customer service, and NEVER use a franchise/kiosk in-person for service - make sure you're at a corporate-owned store! Even then, some stores might have incompetent staff. I've been lucky that all of my local corporate stores are pretty well staffed.

So you are saying that your Z3's with wifi and LTE on with AT&T are working as they should?
With LTE off my phone responds normally with wifi on. With LTE and wifi on it will not respond to calls after a 30 minute sleep. It does not show missed calls. Calls go straight to voice mail after 2 rings. Could you tell me what level your LTE dBm's are? Thanks!

I was told not to give them my imie# but, after recvng the minisim I had to call them in order to 'provision' it to work at all and they needed that #. I have never had any problems personally and am assuming this may be because you gave them the wrong #. Again I am only guessing. Oth, if I had had a different imie to give, I would have done so myself.

It is very strange and I am feeling it is more signal strength related than how you provision your phone. (Once it is provisioned correctly.) It seems that more people have less problems when they already have a nano-sim and just plunk it in the new phone. This might indicate that they already had a strong signal from the get go. My old HTC One + get's a better signal than the Sony in the same locations with the same (new) SIM. With the Devilcase bumper on it gets 5% less. My very limited tests yesterday seemed to indicate that it was signal strength related. I am not enough of a conspiracy theorist to imagine that AT&T would program their system to not function correctly with sims that are provisioned with these Sony phones which they are obviously ignoring for some reason. Or am I?

I had all kinds of problems with the Z3 on AT&T. The IMEI caused an issue since AT&T linked it to a flip phone and therefore couldn't provision LTE. I changed it to an old AT&T LTE device and then I was able to get LTE but was having the same issue with calls going directly to voicemail and texts showing up hours later in bunches. I found the solution was to switch off LTE in the quick settings menu. All calls and texts came through and on time while LTE was off. If I needed a data boost to stream, I turned it back on until I was finished streaming. This was while on KitKat. After upgrading to Lollipop, I was able to keep LTE turned on and calls and texts still arrived on time.

I use data rarely. Mostly wifi. If I don't leave LTE on, my phone reverts to wcdma preferred. And why can't LTE just work without me having to constantly turn it back on? What bugs me is having the APN settings greyed out. I want to be able to turn it off. If anything it seems the phone itself is preventing me from accessing the sim. It feels like I'm borrowing something which contains lots of MY private data. I know my phonebook is stored locally but I also noticed there is no option of specifying the sim or not. Anybody know how to switch APN on and off? In fact, overall even rooted, I still feel like I have almost no power over it. I can't even disable the cellular connection without going full on airplane mode and I do not trust that. I don't even fly so that needs work for sure. Dumb question but could I buy a working nanosim from say 7-eleven that my apn switch will work with?

"Anybody know how to switch APN on and off?"
On my Z3 on OTA stock Lollypop I have an icon in quick settings to turn LTE on and off. Drag two fingers down from the top of the screen. If no LTE icon then select the pencil icon at the top and select the LTE icon. There is also a mobile data icon switch there.
To turn off your radio completly you can get the Advanced Signal Status app and select additional info at the bottom and click phone information and turn off radio. Probably a number of ways to do it but that is one.
Sim contact storage was a way to move information from phone to phone. You can still do it but not really necessary with cloud backup and storage. Google does it for me without me having to do anything which I like. I still save contacts to the sim just because I can. Export and import in your contacts app menu.

johnboatcat said:
So you are saying that your Z3's with wifi and LTE on with AT&T are working as they should?
With LTE off my phone responds normally with wifi on. With LTE and wifi on it will not respond to calls after a 30 minute sleep. It does not show missed calls. Calls go straight to voice mail after 2 rings. Could you tell me what level your LTE dBm's are? Thanks!
Click to expand...
Click to collapse
Works fine here. I don't pay attention to the dBm estimates since these aren't measured with calibrated test equipment and vary widely. Those numbers are basically worthless.
The only valid comparison is data performance in a given environment (ideally a difficult weak-signal one) - and at my desk with very weak signal, every phone I've ever used performs similarly to the Z3.

"Those numbers are basically worthless."
True, but we have narrowed this down to the possibility that it might be signal related so it is worth a shot. If people whose phones are working fine would measure the LTE dBm on Advanced Signal Status at the location where their phone sits and works well the most we might possibly see some measure of difference in the phones that are not working. Most of the non-working phones seem to work sometimes so signal strength is the next best parameter to rule out. Thanks!
Here are the screen shots of my phone with LTE on, LTE and wi-fi and LTE off and wi-fi.
How do the working phones compare? Does your CDMA (voice) also go to 0% when LTE is on and GSM = n/a?

Thanks. I think adv sig nfo actually works. I'm amazed actually. I can't find the phone's native greyed out apn switch anyways which really makes no sense.

Nexus 6p LTE broke after Rom update

The basic problem is as follows:
I've got a Nexus 6p on which I dirty flashed an 8.1 update (27 Feb 2018) of ABC Rom over an earlier 8.1 version (01 Jan 2018) of ABC Rom. After that, the issues began. At boot, I'd be on 3g and if I toggled airplane mode off and then on, I could get LTE for about 10 seconds. However, it would then drop back to 3g. It's probably worth noting that my cellular provider is Verizon.
I tried everything that I could think of and/or learn via the google. Such as:
Wipe system, data, cache, and dalvic
Revert to stock
Install different/older radio images
Changed SIM (although still Verizon)
... nothing worked. I've read about people manually configuring their APNs. However, I've got a Verizon SIM, so that option does not exist... as far as I can tell.
I've identified a crappy work-around that allows me to get a stable LTE connection as follows:
Open the Phone's Testing Settings by dialing: *#*#4636#*#*
Tap "Phone Information"
Scroll down and set the "VoLTE Provisioned" toggle to the "on" position.
Then, toggle airplane mode on and off.
However, the reason I've described this as crappy is that doing this results in my phone being unable to make or receive calls. Whenever I try to make a call with VoLTE Provisioned, the call fails and reports "Server Error". Consequently, I generally just deal with the phone working in 3G. On the up side, this work-around does demonstrate that LTE is still possible... with the right configuration. Although, it would be nice if I could get both LTE and phone working vs just one or the other.
I came across this post suggesting that a possible solution is to boot the phone up with a non-Verizon SIM, power it off, and then boot it up again with the Verizon SIM. I'm not sure how this fixes the issue. However, before I go buy a $30 SIM in the hopes that it will fix my issue, I figured I'd make this post and see if anyone has any other ideas how I might correct this.
Any ideas are appreciated.
[email protected]

So after a few months of using 3g, I got my hands on brand new AT&T SIM card. (For what it's worth, it hadn't even been provisioned yet). I went ahead and boot the phone with this new sim card. (I also reset the new APN settings to the default, although it probably didn't do much). After powering the phone down and putting the Verizon Sim back in, I've got my LTE back and all is good.

SM-N9860 - "Not registered on Network" error suddenly in the UK

Hey guys, really hoping someone is able to help me.
Back in September 2020 I purchased the SM-N9860 variant from T-Dimension for use in the UK on EE's network. Everything has been running smoothly since day one, up until yesterday (31st May) where the phone would constantly struggle for signal, flip flopping between "No service" or extremely slow 4g. If I try to make a call I get the "Not registered on Network" error message.
Since then I have done everything I can think of:
- Restarted the phone several times
- Switched Airplane mode on/off
- Manually selected my carrier
- Reset network settings
- Tried my sim in another phone (which worked fine), and tried a different sim in my Note 20 (exhibited the same behaviour of "No service")
- Checked IMEI but it's not been blacklisted
- Tried my sim in the SIM2 slot
- Full factory reset
but none of them made a difference.
Tonight I decided to try and flash different firmware to see if that might have any effect; both TGY and BRI firmwares were flashed successfully with Odin but neither have solved the problem. I'm now at the point where in my home I can see the 4g symbol appear above the network status for 30s - 1min but it never actually loads any data, before returning to "No service". Compared to my fiancee's S10+ which is also on the EE network and easily hits 20Mbps without worry in the exact same room.
Does anyone have any suggestions of what to try next? Has anyone else encountered this?
Thanks,
RBrNx

I've spent some more time investigating this and I am 99% sure it's an issue with the device.
Below you can see a screen recording of the issue that I made this morning while I was out a walk, you can see it goes from having signal but no internet ("Emergency calls only"), to "No service", then to 4g but I wasn't able to even load a website, before it moved back to "No service".
I've also attached two screenshots from the NetMonster app, one is from my Note 20 and the other is from my fiancee's S10+. Both were side by side when the screenshots were taken - mine has no service and her's has 4g.
I've since tried a number of other SIM cards in my phone, including another EE SIM and a Three SIM - both work immediately in the S10+, but neither are able to register when put into the Note 20.
I tried to contact Samsung Support but they were next to useless. The UK support team told me I'd need to contact Hong Kong support "as they have full access and information", but all the HK support could do was tell me to visit the HK Support Center...
I'd love to be able to fix this issue but I'm not sure what else to try
EDIT:
Some more information that I forgot to add - When I am out of the house I can occasionally receive calls/texts or use the internet, so I know for sure that they are all working (i.e EE haven't blocked my account) but most of the time I am stuck with "Not registered on network"
I'm wondering if it's an issue with the antennas, it's almost as if they are somehow weaker or less receptive than they were a few days ago

Does it behave this way when in safe mode ? How about in 3G mode? If it's hardware then Samsung doesn't recognize devices that are from other regions in relation to warranty work. You'll have to test the after sales support of T Dimensions now. Failing that sell it as is on eBay for parts or try and trade it for another device.

I'm using the same device on Vodafone UK and no issues here at all

I'm using an N9860 HK model, also from T-dimension, with EE since last autumn. I have not had any such problems with mine.
I haven't flashed or rooted the phone, but I have tinkered in the service menus in order to gain 5G service and possibly other service improvements.

Yeah, same for me. Changed the 5g whitelist settings but no root.