There are permission with Catalina that have to be set properly, which was not true of earlier MAC operating systems. As I am not a Mac person, I can't be more specific, but if you search these forums, you should find them.
It's as dj_paige indicates, on a Mac click on the Apple Icon then System Preference> Security and Privacy. In the dialog box you can allow LrC to have full access or go to Files and Folders and specify which folders LrC can have access to. See the screen capture.