MMS sending, not receiving

I'm having a strange issue I have yet to find any information on. Here's what happened:

I had my HTC One M8 for about a month. Everything was working fine, MMS sending and receiving, no problem. I only use minimal data, so I keep mine off. I don't like to waste my 200 mb per month. One night while I was sleeping, I became part of a group text, about 30 messages or so. I wake up the next morning, see the group texts, turn on my data, and it begins downloading messages. They started coming in pretty quickly. After about 7 messages, it completely stopped. Every message yet to be downloaded continued to say "downloading" and never progressed. I left it this way for days, nothing changed.

I eventually deleted all of those MMS messages and sent a picture to a friend, asking if they received it. They did, could describe the picture to the detail to me, but when they sent me a picture, same thing: "downloading..." never to complete.

I have tried hard resets, changing the VPN settings, even wiping the dalvik cache. Nothing. I still get 4G LTE just fine, nothing is different except being able to receive any and all MMS.

Any ideas?