How do I fix "(-9820) Unknown error for Genius" when trying to sync library on Mac?

Apple Music Genius results can’t be updated right now. An unknown error occurred (-9820)

Ive just made the jump from PC to Mac (as everything else I have is Apple)

I have a lot of personal music files and used to use iTunes on the PC to sync library.

This is still working on the PC but on the Mac the Music app constantly throws the (-9820) Unknown error for Genius when trying to sync library.

Please help!

[Re-Titled by Moderator]