Sorry to hear that. It could be several reasons
- Card issuer/ bank Denied - Card issuer/ bank refuse to complete the payment. Kindly contact with your card issuer / bank for authorization this particular transaction
- Your card issuing country is different from your shipping address or you are using the card not in issuing country.
- Card declined due to insufficient fund, invalid card type (Amex & Discover).
If none of the above applies, you can try checkout via PayPal.