reb1971: Any idea why this would be happening? Thanks in advance for your help! :)
chrishopeuk: Just got it working again. Install by downloading the back up file rather than through GOG galaxy. Worked for me. If you are reinstalling keep the old config file for your settings.
Galaxy is the default method of installation from GOG these days. Manual file downloads are for our backup copies now, too, while Galaxy is the primary install engine for GOG. You can still install manually, if you like, but in most instances the manual files are a few days behind the Galaxy updates & patches--or, as you discovered, of a lower priority to GOG than Galaxy.