But only for a moment. I've spent most of today trying to fix things, or at least trying to figure out what problems need fixing. One of the problems has generated a comment thread on a vendor website, now at 44 comments, and I think after all that work I found the problem in an interaction between my code and Microsoft Azure Functions. If I'm right, the confirmation will come around 3pm.
Naturally, I haven't had time to read any of these:
I wrote the intro to this post around 2:45 and had to pause for a while. It's now 3:25, and I appear to have solved the problem. I will now document the solution and apologize to the vendor. Fun times, fun times.