Can't send/receive MMS with Galaxy S8 after new SIM exp network upgrade - a Solution
Like many others here I started having issues sending/receiving MMS (group messages or picture messages) with my Galaxy S8 last year. When it started last year I had to change the network settings (from Automatic to CDMA) and reboot to send/receive MMS and then reset it back, a few month later, I only had to turn WiFi off to send/receive MMS from anyone using the phone's Messages app. The exception were my wife's (old J7 and new G20) phones - for some reasons those messages always went thru due to a previous install of FB Messenger+ and the chat setting. I had no problems sending and receiving MMS to and from her.
Anyways, I just went thru the new expanded network SIM upgrade this last weekend and when everything was done I couldn't send or receive MMS with or without Wifi, except to my wife's phone. Strange. The ##72786# feature no longer worked after the SIM upgrade. The person who helped me looked up some community forums and it was kinda suggested that it is a hardware issue with the S8. However, someone posted that installing a different Messaging app resolved the issue. They mentioned the TEXTRA app. I was hesitant but desperate enough to install the app and make it the default. AND GUESS WHAT? IT WORKS!!!!! With or without Wifi my phone is able again to send or receive MMS. So, no hardware or network issue - just a problem with the Messages app that was pre-installed on the phone.
Now, in Textra Settings I found one little interesting setting under MMS Fixes: called WiFi Fix and it is described the following way "Set this to temporarily de-activate WiFi when sending or receiving an MMS. This makes MMS work with T-Mobile, Xfinity and some AT&T users." Interesting, right? I did not enable it since it is working over Wifi just fine but when it was enabled I noticed that WiFi turned off when an MMS was received or sent, just as described.
So, there you have it. I have been using the TEXTRA app since last weekend and it works just fine, no issues.
Side note: even after the SIM upgrade to the expanded (T-Mobile) network, the S8 still runs only on 4G LTE (and the letter symbol for it is sooo tiny, very hard to see). For 5G data you would need a phone with 5G hardware.