I haven't heard of cards with 17 numbers. Perhaps try calling your issuer? Did you try the patreon page? Let me know if nothing works I will try and help.
Nope, nothing works. Not Patreon, not itch.io, not PayPal on both of those. It's definitely not a problem that my issuer can solve it's just that it's a prepaid debit card which isn't accepted by most payment services. It's basically a safety mesure and as long a site doesn't offer bancontact, Klarna or any similar kind of direct online banking payment method there's not really anything I can do. The only thing I could think of would be to directly submit the payment to the bank account that you have linked to itch.io.
Hop on the discord and message me, let's sort it out https://discord.gg/YNg2nXUs.
Discord name is stronggirls