There are several possible issues. Check to see if any of the below issues are relevant. A. Make sure you have entered your personal information correctly. Make sure the information you entered is exactly the same as the information of the card account holder. B. In case of credit card, check your CVC code and make sure it is correct. C. Make sure your card can be used for international purchases. D. Some VPNs may cause problems because the IP address is blocked by our payment provider. Try switching locations or turning of your VPN. E. Clear you browser cache if problems occur on the checkout page.