If you are trying to pay by credit card and get an error, it may be due to one of these causes.
Check the data entered
This is usually the most common error, check that the 16 numbers on the card are written correctly, as well as the expiry date and the CVC code (located on the back of the card).
Check that the card is valid
Check that your card is active (when new cards arrive, they usually need to be activated at an ATM) and that it hasn't expired.
Some banks also require them to be activated specifically for online purchases.
Proxies of companies or organisations
Some companies and organisations channel web traffic through a proxy, which sometimes filters and blocks external web requests.
If this is your case, read below. In addition, many times the computers of these organisations only have a specific browser, which is old and may also be the cause of the failure.
In order not to lose your design you can choose Paypal as payment method
Paypal also allows you to pay by card, even without registering, you can choose that payment option and enter your card data from Paypal.
Since 1 January 2021, the new European PSD2 regulation obliges banks to verify all online payments with a double authentication factor.