I can’t activate my iMessage

https://support.apple.com/en-us/HT201422

check that :)

but also: your data might be registered as spam-address, then call AppleCare for help -

Try the steps here:

https://support.apple.com/en-us/HT204065

Try signing out of your apple id and sign back in after a hard reset. Then sign back in to i message

hope this helps