Hi Helptb,
Welcome to the Apple Community, where some of us do the best we can to help each other troubleshoot :)
Your Apple ID is the account you use to access Apple services,
such as the App Store, Apple Music, iCloud, iMessage, FaceTime and more.
If you have changed your Apple ID, or your Apple ID password recently,
you may need to update it for everything apple you use .
If so: this article can guide you:
What to do after you change your Apple ID or password:
https://support.apple.com/en-au/HT204071
If that is not the solution, you might want to try this article below from Apple Support.
If you can't sign in to iMessages on your iPhone, iPad, or iPod touch
https://support.apple.com/en-au/HT204065
If you still need help:
There is a "Get Support" link to Apple at top right on this discussion page.
Hope this helps you enjoy using iMessage ok :)