Solution: try a different card or a different payment method – PayPal.
Declines can happen for a variety of reasons. When we submit a charge to a bank, they have automated systems that determine whether or not to accept the charge. These systems take various signals, such as customer’s spending habits, account balance, and card information like the expiration date and CVC.
Usually, an error message is self-explanatory but for security reasons, some errors provide just a generic message like “The card was declined”
In that case, you should check with your bank whether your card is suitable for internet payments.