The last two upgrades seem to really screw up my LRC and Photoshop. I get the message that cannot open the catalog Lightroom Catalot-2-2-2-v10-v11.lrcat because another app is using it. Which it is not. I go to the files and find no lock catalog...I find one for previews and several zip files (which I assume are backups) and one that appears to be the main one. Dont know what to do...when I opened Photoshop it was as if it was brand new.
What is going on..I have Monterey 12.5..on my 2018 imac.
As an example I have illustrated a .LOCK file in the screen-clip from @DdeGannes
It will be found next to your other Catalog companion files-
You should NOT try to open files in a Backup location. If your LrC is saying a Catalog is corrupt, you need to extract a catalog from a backup .ZIP file and copy it to another location (eg. the Pictures folder) where you can 'open' it by a [Double-Click].
Next time your catalog needs to be upgraded, please note that you can actually rename the new catalog in the upgrade dialog, so you won't get something as useless as 'Lightroom Catalog-2-2-2-v10-v11-v12.lrcat', but can change that to 'Lightroom Catalog-v12.lrcat'.