This may have been a red herring, with the actual problem being the lower case issue. And also a total misunderstanding on my part of how the Update Manager Endpoint works:
Thanks for the detailed response. Of course, me not being a developer, I had more trouble than necessary. I didn’t expect the trial to generate the need for so much help. But I did know it would be a miracle if I got it working.
You only learn by doing and you never know, this thread may help someone else in the future.
No problem; I appreciate your sticking it out. I was feeling kind of thrilled when you posted your success screenshot. You (and others) have pointed out which areas are more difficult to understand and that’s valuable information that can be incorporated back into the design.