Talked to UGS
A more useful datapoint for everyone.
I saw "Denied" on mine too, so I called Global Services. They looked at the itinerary and in my case the issue was that there had been two simultaneous upgrade requests made, and it was denying the second one. That generated the "Denied" message.
She removed the extra request, and it now says "Waitlisted" again.
It seems they are somehow doing all these upgrade requests manually, because they refer to "they" or "he" for the upgrade request being made.
In any case, if you see "Denied," it's worth calling and having them clean up the PNR to ensure there's only one upgrade request on record.
Good luck to all!