iMessage login unknown error

I am having trouble logging into my iMessage account on my Macbook Pro. I enter my login details & it searches for a while then it returns an unknown error has occurred. When I cancel that, it pops up a box asking me to log into iMessage but the user id is an old email address I have not used for over 5 years.

iMessages works fine on my iPhone using my correct login information. I have tried several corrective actions I found but none has worked so far.

I'm thinking about creating a new Apple id but I don't really want to do that.

Thanks,

Rick