I forced quit and tried again, same problem.
When LrC is launched, when a catalog is created or opened, a lock file gets created. The lock file exists as to prevent a catalog from being open in more than one instance. When LrC properly closes that lock file gets deleted. If you force quit LrC, or LrC crashes, that lock file does not get deleted. If the lock file exists, then LrC will not open the catalog. In theory you should get an error message, but maybe not.
Now this does not answer your initial problem, but as you forced quit, check for it:
be very very careful to delete the correct file.
. I closed the app and saved the catalog.
Please expand on that, the and saved part, the catalog does not get saved upon closing, it is a database that gets altered with each and every edit.
on a new MacStudio with M1Ultra chip.
So MACOS Ventura, did you give (when prompted) LrC full disk access?