Cannot open existing catalogs after Big Sur/LrC update

[photobyrob1]

Updated my MacBook Pro to Big Sur bc the LrC updates suddenly made it incompatibale with the older OS. But now that I have the latest updates I find that LrC will not open with any of my existing catalogs. Only if I create a new catalog will it open and run. I have literally 10's of thousands of photos across a multitude of catalogs for this year alone, most of which have gone through my culling and editing workflows, only now I have no access to all that previous work. I worked thhrough many of the discussions here and tried the prescribed fixes, but nothing has worked. So what now? 

[photobyrob1]

Oh, and when I try to unzip a backup of one these catalogs, I get a message that says the zip file is empty.

[dj_paige]

I find that LrC will not open with any of my existing catalogs

Exactly what happens? Describe in detail. If there is an error message, quote the exact complete unedited error message.

Oh, and when I try to unzip a backup of one these catalogs, I get a message that says the zip file is empty.

Not something LrC or your operating system would do; more than likely this symptom, and your other symptoms indicate a hard disk problem.

[GoldingD]

Was your previous MACOS older than Catalina?

If so, see:

https://nektony.com/duplicate-finder-free/folders-permission

Files and Folders, make sure Lightroom Classic is included, make sure Lightroom Classic has right to all the volumns shown, tyically user created issue with removable.