Lightroom stuck on 'Syncing 1 photo' and none of the fixes described here have helped

[paulc40512238]

My Lightroom (4.2, on macos Catalina 10.15.7) has been stuck on 'Syncing 1 Photo' for some time now.  I realize that this is a common issue, and have tried the fixes I've found here and elsewhere:

- Removed and reinstalled CC and Lr

- No items appear when I click 'View' next to 'Syncing 1 photo'

- No items in 'Deleted'

- No 'Sync Issues' in lightroom.adobe.com

I'd be fine ripping the whole thing out and starting over, as I have another issue whereby Lr now refuses to use my NAS as local storage, but I can't find how to completely remove Lr and all of its preferences and associated files - I've tried the Adobe Creating Cloud Cleaner tool, but no joy.

Any other ideas?

[paulc40512238]

Nevermind - found the local cache (Lightroom Library.lrlibrary, which existed even though I'd set Preferences to store the originals on a NAS share), renamed that, restarted Lr, and it's now healthy.