Installed the update a couple days ago. Could not import any thing into the catalog. Presets gone and nothing showing in the library. Rolled back to previous version and it works fine.
In your current working catalog, in preferences, have you selected to store presets with catalog?
While having that selected, the upgrade of the catalog should have honored that, but perhaps it is not?
It was selected to store with catalog. the bigger issue was that version 12 was unstable and I couldnt get it to do anything all besides open up
If you provide this information, it will help.
On the nothing showing up in the Library,
Did LrC perhaps select the wrong catalog to upgrade? An earlier one?
Or, as their is nothing, did it create a brand new catalog, not a copy at all?
Sounds like your preference file is, or was, corrupt.