"Unknown error" message - Apple ID password problem when accessing iCloud preferences

"Unknown error" occurred when entering Apple ID password to access iCloud preferences. Password works everywhere else - including to sign in to this Community. Is there a glitch with a current upgrade that causes password problems with iCloud? I don't remember previously having to enter the Password when accessing iCloud Preferences.

First I received this message when trying to connect to iCloud:

This Mac can’t connect to iCloud because of a problem with “my apple id”.

Open iCloud preferences to fix this problem.

Then when I went to open iCloud preferences, the "unknown error" appeared when I entered my password. Again, am having no problem with Apple ID or Apple Password anywhere else including accessing iCloud preferences on my iPad.

Thanks,

Debra

Mac Mini

High Sierra OS 10.13.3