Why won't my iMessage work with only one contact in my phone all my other iMessages send and they just got an iphone but all their iMessages are sending also. I've tried restarting my phone, deleting messages, contact, restarting network

I know this is 3 years on but it looks like there are a lot of fixes that do and don't work for different people. Like others my problem was triggered on just one contact after our phones were forced to send SMS to each other while 1 phone was out of service briefly (or in some peoples' case they were on the phone while sending message, etc).

This fix worked for me after trying all the others without success!! You will need to add yourself to your contacts before trying this. Just create a new contact with your number.

1. Compose a new message. Add the problem contact, and add yourself, creating a group chat
2. Send message in the group chat. Should automatically send as iMessage
3. Go back to your regular thread with the contact and send another message. At this point it should have changed to iMessage again

You can now delete the group chat and everything should stay normal.

Hope this can help someone else!