It might be the below reasons:
1. Card info are incorrect. Please kindly check expiration date, billing address, and security code (Security code on the back of your Visa/Master card).
2. Card issuer bank declined your payment.
3. No enough balance on the card.
4. Shipping address and Billing address are inconsistent.
If possible, we advise you to try paying with PayPal or other supported payment methods.