If your card is not working and you are getting an error, its most likely because of 2 reasons:
#1. you entered incorrect address or billing details, if this is the case, simply try again and make sure the billing details are 100% correct.
#2. You don't have enough credit limit to make the purchase. - in this case, you should hold off on your purchase until you do, or use a different card.
If you know for a fact you have entered the CORRECT billing details and you have enough limit on your card, simply contact support and we will send you a custom payment link for you to pay through using a different merchant processor.