Paymongo not accepting my payment

I tried using 3 credit cards and a debit card. Paymongo messaged "The card type used is not allowed. Please use another card or try a different payment method." I'm in US and have ordered with CC successfully to this store before. So before I complain to the store why they are losing legitimate orders and business I want to give Paymongo an opportunity to fix this in a timely manner.