Hi there, LGStylo2. We can guarantee that MMS will work while you are using the mobile data that we provide. Usage while connected to WiFi also depends on the phone and software updates.
Howdy! I just posted about what I think is the identical issue, also on an S8.
I have found if I change the phone network from "Automatic" or "CDMA/LTE" to "CDMA" (which is 3G) then it works but slowly. And obviously since I am paying for 4G, I want to be able to use my LTE without constantly toggling the Wi-Fi on and off.
Sorry I don't have a solution, but wanted to let you and Boost know that it is not just you. I am having the same issue, and it also started maybe a month ago but took me a little time to really recognize and diagnose.
so its October 19th today and same issue is going on, I have perfect 4g LTE all bars, perfect WIFI, I can send and receive phone calls, voicemail and texts just fine, but MMS still does not work I can not send or receive them, sending fails after several minutes of the hamster wheel spinning, and still get the "download message" banner when some one sends me a MMS. I went to a boost store today and they said it was a known issue, so their is still no fix, I tried the whole PRL, profile update and the ##72786# reset and still no resolve. the lady at the boost store said so far that she has been met with android users s9 and older with this issue. its completely ridiculous that this is still going on for over a month now from what I can tell, I didn't know it was happening that long because my phone started doing this last week I have an s8