iMessage not activated on iPhone X & XS, And I was trying to activate but the message showing iMessage an Error Occurred During Activation Mac what was the issue?
You could try to reinstall and install iMessage on your iPhone again. If the problem still exists, you may need to check your iOS system. Or you can try to use iOS repair software like TunesKit iOS System Recovery to solve your problem. Your problem will be solved with ease without losing your iPhone data.