iMessage problem

Have you tried signing into Setting Messages/FaceTime?

Messages - If you get an error when trying to activate iMessage or FaceTime

Messages Troubleshooting

Hey Eric,

I tried this and still nothing. I have also tried the resetting carrier settings, removing and putting SIM card back in, and signing out of Apple ID and cloud as a whole. When I did this last part, it now has a difficult time logging back into apple id and I lost all of my contacts. I also confirmed I can get SMS (it's the only way people can reach me since imessage doesn't work)

Have a call with apple support later will let you know what I find out.

I had this same problem in my iPhone X when upgrading from 13.0 to 13.1. I found a new threads on here with the same issue. I tried everything including restarting, turning iMessage off and on, resetting network settings, logging in and out of iCloud. As a last resort I have reset the iPhone to factory settings and restored from iCloud backup. iMessage worked immediately after restoring from backup.