Please check you have followed the below process:
1) added your payment card to the drop down credit card box
2) selected the Visa debit or MasterCard debit drop down option
3) add long card number
4) add 3 digit code on the back of the card
5) add your address where you have registered the payment (Visa,MasterCard & Discover) card
6) agree to terms and conditions and click proceed to confirm and complete your transaction
You will need to check that the billing address on your order must match the billing address associated with your card. You may also wish to try on a non-VPN connection. You can verify your address on file by calling the phone number on the back of your card. Additional decline reasons may be an incorrect expiration date or insufficient funds. Please verify all prior to making a purchase, also if you have tried with the same card more than two times your card issuer may block your card from transacting until you contact them directly.