I ported to three on Friday and number transferred yesterday. Was able to activate and use iMessage yesterday. It has since de activated and whenever I try to reactivate it fails. Constant loop. I have spoke with apple and everything is okay their Side. It is not the phone as it works fine with my second line and when I put the sim in a different phone it has the Same error.
HI @David_43862 and welcome to 3Community 😊 Are you still experiencing difficulties using iMessage? If you are I'd be happy to help you with this, let me what model iPhone you're using and if the phone number updated from the temporary Three number to your number since your number transfer was completed.