My saga continues:
Sent another in-app Help message/question yesterday. A few minutes later, I got a pop-up saying I had a response, but the actual message has never appeared.
Now an additional problem: Looking at the online account for the Amex card that was not accepted when I tried to add to my Uber Cash shows the card has been debited for the transaction. But my Uber Cash balance does not reflect the payment.
Very frustrating!