If you have encountered an error when using your Amex credit card during the payment process. 

During the failed process, no amount is deducted from your credit card.

Please kindly try the following method to resolve the payment process.

(Please refer to the screenshots example)

If you have any unpaid invoice due to the error process, you can view it in your profile billing page.

To proceed, click on the red Unpaid button.

After that, you will be directed to the invoice page. Now select American Express (via PayPal.com) as your payment method.

Then click on the PayPal checkout logo on the top right corner.

You will now come to this PayPal page to fill in your details. 

(Please kindly note you don't need to have a PayPal account to complete the payment)

Just fill in the necessary on your Name, Email, Contact, Amex Credit Card and Billing Address. 

After that, check on confirm via the Privacy Policy and click Pay Now. 

Once completed, your payment will be successful.