Declined transaction / Card doesn't support 3D Secure

Hi Support Team!

I'm trying to place an order for a doujin using a prepaid mastercard - no offense, but I don't want y'all to show up on my credit card statement :)

I've placed orders successfully in the past with prepaid cards from this suppler.

But the checkout has started reporting "There was a problem. This transaction has been declined." even when all the card details are entered correctly.

I contacted the card issuer, and they told me they saw a "test transaction for $0" but no further transactions coming through - failed or otherwise. They tell me this is a sign the vendor requested 3D Secure authentication, which they don't support.

I'll admit my account might have had a few failed checkouts in the past, thinking a prepaid card had slightly more credit than it does, so perhaps my account got flagged somehow?

In any case, I'd like to request improved support for mastercards that don't support 3D secure - thanks!