Change name of the Catalog impossible?

You cannot change the name of a catalog while other activity is going on in that catalog e.g. face recognition or other media analysis.  In fact, you may not be able to change the name if the catalog is the currently open one.  Try the following:

• Create and open a new empty catalog from File>Manage Catalogs.  Then enter the Catalog Manager again, and try to select and rename the catalog.
• If that doesn't work, close Elements and rename the catalog folder using your OS (Windows File Explorer or Mac Finder(?) )  The default location for your catalog is:  C:\ProgramData\Adobe\Elements Organizer\Catalogs