Multiple iMac Accounts Each With Own Apple ID and iTunes

Evening All!

I recently bought an iMac and have created log in accounts for all the members of the family. My wife and I have had Apple IDs for years and our own iTunes data. When we moved our data from our old PC to the new iMac, I didn't transfer my music from my laptop - just my wife's from the home PC. I recently added my music from my laptop, and now my wife can't download new content she has purchase - a message comes up saying that "This computer is already associated with another Apple ID..." and that it can only be changed every 90 days so can't download for 15 days. Although the items show in the library with the cloud symbol next to them, if I check for available downloads it tells me that none are available!

Each person with a log-in and an Apple ID does have access to their iCloud, Photos, Movies/TV shows and Apps etc so it is just Music that is not playing ball.

So, if you're still reading (!), my question is how do you have 2 separate Apple ID accounts on a Mac/iMac and access all the data associated with that account?! Is it really only possible to have one Apple ID with associated music? Or how do I set it up so that we can each have our log-ins and own music available ?

I'm running Catalina 10.15.6 (with a pending update tonight too).

Many thanks!