Unable to sign in to Apple Music on my MacBook Pro despite having an active Apple One subscription

This happened about a week ago. One day I just couldn't sign-in to Music. However, it was showing an effort in that little message window at the bottom of left hand panel to download my music from iCloud. When I select the Radio option in Music I get a message on-screen saying there had been a problem and to try later. I've been seeing that message for days. Any other choices made on the left-hand panel return the same message. I should add that my iPhone is unaffected. I have full access to Music through the Apple One account.

[Re-Titled by Moderator]