Replying to an old thread-- did not think my issue warrants a new one, but my issue is not *exactly* the same. I'm having trouble getting past the payment screen in a *A award booking:

If I enter a credit card number, even before submitting payment, it errors out and says: Your credit/debit card is not valid for this fare. Please try again with another credit/debit card, or select another flight and/or fare.
If I attempt to use Masterpass, it errors out and says: We cannot process your request right now. Please try again later, or get in touch with your local Singapore Airlines office.

As far as I can tell, this issue is not happening for SQ award bookings, but I did not complete payment for an SQ booking as I did not need one.

I've tweeted to SQ and submitted screenshots; is anyone else having the same issue or am I going crazy?