Try starting from the
command line (to get it started, them you will fix the Location for a normal start)
Use the library located at the specified path.
Code:
calibre --with-library <"path">
Then use the create/switch option on the Library Icon: USE EXISTING
to set the new location
And also use the REMOVE LIBRARY <old name/location> to stop Calibre from even trying. (this only removes linkages from not in use libraries)