When I open Lightroom my catalog shows zero in Catalog, folders, collections etc. All of my pictures are still in the system but I tried to move some files to a folder and everything went blank. Could the move have caused this?
As you're not able to open the catalog, could you try looking at the location mentioned below for both (MacOS & Windows) and try opening the catalog from there & let us know if it works?
/Pictures/Lightroom (Mac OS)