Samsung Galaxy S8 Using Messages and Microcell Can't Send Pictures or Video

There was a recent update from Samsung, and I'd hoped that following this, I would be able to send MMS. It did not fix the problem, but here's something odd. I thought maybe the update hadn't finalized, so while I had two MMS "sending," I rebooted the phone. Almost as soon as it restarted, the two messages were sent, and immediately received. However, after the restart was fully complete, attempting to send MMSs again, resulted in "sending" until failure. This seems to suggest that something that wasn't immediately operational is preventing the sending. To further test this, I took the phone to a location far enough way that it lost the microcell signal, and was able to send messages.

Turning off the microcell is not a good option, as it prevents incoming texts and calls from being received, and obviously disrupts the other users, as cell service is otherwise very weak. Since this does not appear to affect iPhones and older Nokia phones, why would the microcell have issues with the Gamaxy?

Sorry. "Galaxy," and of course, why was this problem not evident for a couple of months, but has become a problem in the past 6-7 weeks? This makes it seems like it is not the microcell, but something that changed in the phone.