That's frustrating, sorry about that! One workaround I have used in this situation in the past is to place the order while making sure the save card for future checkout is not checked.
If that still doesn't work, please reach out to email@example.com. Our support team can look into your card number and remove the block on the payment gateway. Sometimes it comes up as a safety net and it is not your card's fault at all. Anyways, once you reach out to them with your information they'll be able to clear it up.
Keep us updated and let us know how it goes!