My iPhone 6 stopped being able to reply to MMS messages on Feb 1st. I think this happened after I added some security settings for my son's safety. I can receive MMS but when I reply I get not delivered. The upload bar gets 90% of the way across and jsut hangs before it chows the not delivered message in red.
I have verified all the settings are turned on for group and for MMS. I have deleted the original conversation and tried to respond with a new text and that doesn't work either.
iPhone 6, iOS 8.4, iMessage works but not regular MMS