Catalina's Music library cannot be saved (with no syncing device around).

We open Music on my wife's iMac using Catalina, either by clicking on Music or by clicking on her Music\Music\Music Library.musiclibrary file. (or using option to open that)

I don't think her playlists are up-to-date when we do it.

Her iPhone and iPad are not around.

I see a message saying that it is updating the iCloud library, then a minute later, I get the window saying:

The Music Library file cannot be saved. an unknown error occurred (-54)

I have checked read/write privilege for that musiclibrary file, and went to my Music directory and set read/write privilege for *all* files in its subdirectories. This has been happening for a couple of weeks now, maybe since I updated my Apple Music to family (She is our family organizer, Apple Music was mine).

I keep finding links about this error expecting synchronizing and iTunes, neither which is being done here. Tried *lots* of recommended links which expect that. Some recommend deleting the itunespref.clist file, but we don't have iTunes anymore. Is there a new .clist that I need to find and delete?