Hello @MarkRash,
That's a great question, while I have used Catalog for over 4 years I have limited experience with the "Program" listings (we almost exclusively use single Courses). Based on your troubleshooting, it seems like the system is resisting a Certificate download based on the original settings when the student enrolled.
Unless there are multiple students encountering the same predicament, my team's suggestion would be to provide them with a manually generated certificate / completion letter & apologize for any inconvenience.
Best,
Kevin Hitt
USF Corporate Training and Professional Education