Can't find how to fix "stuck" sync when preferences show nothing syncing

Running latest LRC on Windows 11 laptop.  I don’t sync from LR, which I rarely use, and haven’t synced anything for a long time from LR mobile. (LRmobile photos are synced into a “From LR mobile” folder in Collections, none of which shows any obvious issue or activity.)  I’m not aware of other sync activity, 

Once or twice before, when sync has gotten stuck on a photo, I remember being able to fix this in the Preferences sync settings.  There’s nothing there now showing any sync activity at all, so nothing to delete. No help or search suggestions are useful; they involve different kinds of sync problems and mostly give only Apple and/or LR instructions.)  

I’d like to get rid of the error message that appears every time I close LRC, and eventually I’ll have other mobile photos to add to some collection.  If any more info is needed, please let me know.  I’m sure I’m missing something obvious and easy.

Many thanks.