Sonim XP3 can't send or receive multimedia or group texts even with 4G or wifi on

My Sonim XP3 is awesome, one of my favorite phones I've ever had, BUT: the only thing that annoys me about it is I can't receive texts containing multimedia, or group texts. Instead I just get a message saying "Couldn't download..." and even if I turn on data and/or Wifi, I still can't download them. Needless to say I can't send them either.

It’s a 4G phone, and my previous flip phones were even less capable and even they had no trouble with these kinds of messages, even with the data turned off.

Anyone know what’s causing this issue or how to solve it?