These instructions do not work:
https://developer.apple.com/support/apple-pay-sandbox/
AT ALL.
We setup the sandbox account. It's enabled for Apple Pay. We're signed in on the test device (iPad Mini 4) running iOS 11.2. We've tried adding every possible card type from that list, all fail with "Could Not Add Card: Try again later or contact your card issuer for more information"
Our region is set to US.
Is it possible that Apple's entire Apple Pay testing system is just down and has been for months?? Every thread I find where people discuss this issue has no resolution.