Just want to report that payment with a valid Discover card failed, incorrectly citing an invalid CVC, oddly. Quadruple-checked everything - no problems in the data. Switched to Visa - no problems. The Discover card is not taken by some vendors, and I suspect that is what’s going on, but there is no warning, and the CVC was definitely valid, so the error message is spurious.
Thanks - I have to say that the programming on the Payments thing is excellent. A really smooth interface, IMO. Very impressed.