Error ’AMEX Unavail’ when attempting to authorize American Express Cards

Summary:

Error AMEX Unavail when attempting to authorize American Express cards.  

Cause:

This message is returned from the credit card processor.

Solution:

Contact the credit card processor and ask why they are returning this response. The problem is usually that the credit card processor does not have the merchant’s account configured for AMEX processing on their side, but the processor will need to confirm.