I messages won't work with 1 friends number why?
I messages have stopped working with one friends number either to send or recieve for either of us. I messages are working without problem from and to both phones wifh other numbers
iPhone 5c
IF you can imessage other people except for this one contact, then the issue is with their phone and not yours.
If you can't send or receive messages on your iPhone, iPad, or iPod touch - Apple Support