iMessage is not activated on iPhone
why did my iMessage is not activated
[Re-Titled by Moderator]
Original Title: iMessage
iPhone SE, iOS 15
Did you already try the general troubleshooting tips mentioned in this article?
If you can’t turn on or sign in to iMessage or FaceTime on your iPhone - Apple Support
Also make sure that no VPN or Firewall is enabled, and Apple servers can be reached.
If this does not help to activate iMessage, please contact the official Apple Support and ask them to look into your personal data and settings from their side.