MMS Not Working

[Windows Central Question]

I have a Lumia 640 still on windows 8. I recently had to factory reset my phone and now when I try to send a picture it won't let me and when I receive a picture I just get a text that says "Oops! The media content you're looking for isn't there anymore." I receive regular text fine, just MMS not working. I do have a Tmobile 640 and I'm using AT&T now, however, it's my phone is unlocked and was working before the factory reset. My data and all is turned on. I have no idea how to fix this.