Another client of mine has an invalid printer issue. They are getting the error in GL 9.3B (210331) but NOT AP 9.3B (201019). They are not connecting remotely. Similar to my other post above, it's a Sharp Network printer. This client is using Windows 10 and it started when the IT person changed her default printer to the Sharp.
Workaround was to change the workstation option in GL to print to a PDF printer.