Please check the following as they're often the causes of the problem:
- Check your web browser to be up to date
- Clear your cache
- Try a different device or use a different browser
- If the payment page is producing an error, check the billing address you've entered is the same address as your bank. Be sure to also check for any authentication notifications your bank may have sent you.
Hopefully trying the above resolve this error for you. If the problem persists please Contact Us so we can investigate further.