I've been having issues adding my American Express as a payment option.
Amex is available in the drop-down list, but every time I add my info, I get a message in red below the credit card number field, telling me its not a valid number.
It's an American Express Corporate Card.
It has 15 digits on the front, but an additional 3 digits on the back (total of 18).
I've tried both combinations, and it always tells me it's wrong.
Has anyone else had a similar issue?