Network and app issues after UI 4.0 Android 12 Update

[Mangofirst]

I have a Galaxy S21 5G (S21+) and so does my husband.  After the Android 12 update, we are both having issues with network data.  Phone calls and normal text messages are fine, but MMS are coming through with the little "No subject/Message size/Expires" download message, message.  Also, on all browsers and apps that use data, unless I'm using separate Wi-Fi, nothing works.  On browsers I get the "No internet connection" message across the top. 

The connection issues have been sporadic.  Sometimes I have a data connection, and sometimes I don't.  Restarts sometimes help and sometimes they don't.  I have removed/reinserted the SIM, cleared cache, restarted, hard restarted.  I have not cleared the partition cache nor have I done a factory reset.

[Kieranxcx]

I'm also having these problems, specifically the airplane mode one! Samsung support have tried multiple times to tell me its an issue on the network providers part despite it very obviously being software sided.

[Hayden_]

Have you tried to disable 5G network mode?

Settings, connections, mobile networks, network mode, change it to 4G/3G/2G

This change solved my problems. To test it, I enabled 5G again and had the same problems so I reverted back to 4G. All good now. 

[Kieranxcx]

I changed just before commenting here to add my voice seeing as Samsung are in denial about the problem for now. And yeah immediately afterwards it started switching to 🚫 and notifying me that my network (Vodafone UK) wasn't available. Its on an off daily since the first android 12 public release but tonight its been at its worst and even resulted in me getting my PayPal account locked from repeated resends on 2fa texts!

[Hayden_]

Yea surely they couldnt get the 5G stuff correctly. Until the next patch we are doomed. Whatever they did, my phone doesn't even connect to my 5G WiFi modem anymore.  

[Kieranxcx]

OK it's been around 18 hours since I've done your quick fix and I must admit, aside from the initial one immediately following, there's been no more episodes of a total signal blackout! As others mentioned it's ridiculous we have to disable 5g to make our 5g phones work so I really hope Samsung find a fix asap but thank you for your advice! It's the best fix right now.

[hasham11]

I've always had 5G switched off, as the network for 5G isn't that strong at my work place. But I am still having this issue. Although switching off dual sim mode and using a single sim seems to have done the trick and I haven't faced any network drops in a couple of days, but the moment I switched on the second sim, the issue came back. 

[Kieranxcx]

Yeah I noticed that it's messy with the dual sim feature too! When it was fluttering connection I opened sim manager and it was flashing up that I had 2 sims inserted but I've never once used a secondary sim! Samsung massively dropped the ball on this and its so disappointing that 2 updates later its still not been fixed.

[Mangofirst]

I didn't even realize I was in the Samsung Euro community until you used the phrase "stuffing up." I'm in the U.S. but we are having 5G issues as well. I think it's from the carriers making things *actually* 5G. My problems magically solved after about a week or so of it.

[Looooooka]

Same problem since the update. Losing connectivity and notificarions for apps are screwed. Fb shows 8 notifications. I open it...notifications not showing even after refreshing. The app has to be closed and reopened for them to show up. This always happens on wifi. Any wifi. Where the hell is an update. At this point an option to revert without manualy flashing would be expected as well. This is literally the worst Android experience I've had on any device. Phone, tablet or smartbook and the first one where the device in question was a Samsung device. 

[BBSquirrel]

After update 12 I too don't have any data working. I can text fine, but without wifi my apps don't work. Not sure what to do. I hope they fix this soon.