MMS stopped working when Wifi is on topic

I'm on a touchwiz based rom and I've always been able to send and receive MMS since my wifi is always on when I'm at home. However last night I received a picture and it didn't download. I tried sending one to myself and it kept spinning for a while and eventually failed. I do have LTE and I'm only able to send and receive MMS when wifi is off and data is on.
I clean flashed another TW based rom and tried sending one right after it booted and it didn't work. I'm not sure what's going on and Sprint chat person wasn't able to help either. What could be the problem? I'm using the stock messaging app btw. Thanks!