I had the no eSIM associated with this phone number, unable to activate iMessage at this time try again later errors. I did get it solved and my issue was because I am using a 14+, eSIM only, and had been having hacking issues so had changed sims too many times. Had to have a senior tech wipe all eSIMs, reset carrier settings and also reset network settings. I still feel that someone did hack my eSims through using my identity. I do still have apps that won’t work correctly and my ATT account app gave me a popup that said MANDATORY UPDATE! Which I have not done. I went to the App Store and there was no update and ATT said my version was correct. I can go to iPhone storage in my settings and it shows 6 documents related to my ATT account that they said were suspicious but I cannot delete evidence for my attorney. So, for now I live with no 2fa on att and candy crush that won’t load videos. The senior tech said they were flipping sims and making nothing work. To deal with sims ask for a senior at apple and for carrier settings call your service provider and update all cellular info. It took some time on the phone but I’ve been dealing with this for 6 months. I will never again buy an eSIM only phone. I’m wanting now to go back to 13 pro max or in the future, I hope to have the more secure iSIM. Also, I am getting a FIDO security key for 2fa. I hope that helps. I am not high level anything, just the victim of siblings who got written out of the will with cia and fbi connections. So this probably won’t happen to you but I hope the info is helpful.