Can't sign into Messages on my Macbook after sign out. error message

DLFrank wrote:

I tried to restart my message app on my macbook by signing out then resigning in after changing my Apple ID password. I keep getting an error message: Unknown error

https://discussions.apple.com/content/attachment/ee955d0d-2c47-4a8a-abde-af17a71e8271

reference:

If you can't sign in to your iMessage account or FaceTime on ...

if no resolve —

Call Customer Support (800) MY–APPLE (800–692–7753)

or on line https://getsupport.apple.com/

Outside the USA—Contact Apple for support and service by phone

See a list of Apple phone numbers around the world.

https://support.apple.com/en-us/HT201232