Hello DanE_6.
Welcome to Apple Support Communities.
If I'm understanding correctly, you are receiving an error when attempting to update the Genius results in the Apple Music app on your Mac. I will be glad to assist.
Let's quit the Apple Music app, then follow the steps under the "Switch to another iTunes library" section in the resource below, to see if you have multiple iTunes libraries:
Switch libraries with the Music app or Apple TV app in macOS Catalina - Apple Support
If you're seeing any other libraries, you'll need to switch to each one, opening the Apple Music app after you select each one. This will upgrade your iTunes library in the new Apple Music app. Once you have done that, open your main iTunes library you'd like to use for Apple Music, then see if Genius results are automatically updated. You can also try to manually update it by going to File > Library > Update Genius:
Use Genius Shuffle or Genius Playlists in Music on Mac - Apple Support
Cheers.