to gooner1969
in my case i had the opposite problem.
ipad2 worked fine for i messages ( using the email address, clearly not the phone number)).8.1.2
iPhone 4 stopped working. this iPhone has ios 7.1.2. cannot do any better.
I solved this by:
1) Restoring iphone as a new iphone.
checked that it worked then. I had successful activation in minutes.
2) then I Restored from a back up( on the computer where I had purchased music). and it still worked after. I presume that it wrote a new config list that was not replaced by that from the restore.
Note:
As a careful guy, i had made a backup of the iPhone on another mac. Restored it from there after that restore, it would not copy music that had been purchased from iTunes store. I had conflicting messages. !!
I deauthorized one computer. Authorized the other ( where music was purchased) . it said computer is authorized, but then refused to copy the selected music when I tried to sync saying the the computer was not authorized!!
another glitch.!!
I had to restore from the original computer where music was purchased!!
Thank you for your feedback. I am in Europe and trying to talk to Apple is beyond my strength