I only ask cus there seems to be a know issue & Zeus knows & has to contact att about it
Discussion
I am not
OK, I got this figured out. The core issue is that Alby forces the recipient to dictate how much is sent, not the sender.
They can't handle invoices that don't specify an amount. I'm not sure why, nor do I understand why the error message I received didn't just tell me that, but that was the answer in the end.