Usually, the reason is a decline from the card issuer.
From our side, we suggest you contact your bank or the credit card company to specify the following:
1. If your card is eligible for international and online transactions;
- If you are enrolled in the 3DSecure program;
- If there are no limits set to your card and cryptocurrency purchases are allowed;
- If you have enough of the positive funds in your account to complete the transaction.
After clarifying the above with the bank or the credit card company, you can make a new payment.