I bought a new PC recently and successfully installed/re-authenticated GPO on it. I also applied all the updates, too.
On my old PC, I had stored the GPO library on a separate HD. I installed that HD into my new PC. When GPO prompted me to select the location of the instrument library, I browsed to that HD and selected the GPO Library folder. But I got an error message, and GPO failed to recognize it as a valid library.