How to activate iMessage
Why won’t my iMessage work or let me
use my Apple ID?
iPhone 8, iOS 14
What happens when you try? Error message(s)?
See if anything here helps.
Messages - If you get an error when trying to activate iMessage or FaceTime.
Some things you can try. Do you have access to another WiFi network where you can try? That has worked for several people.
Try a restart.
Restart your iPhone, iPad, or iPod touch
Try a forced restart.