Why Maybank Amex cannot go through when attempting to purchase Firefly ticket online?

[5140:PaymentValidationError] An unknown error has occured with the form of payment you have chosen. You have not been charged, but due to system failure we cannot accept this form of payment at this time. Please try another form of payment or try again at a later time.

On their FAQ:

1. Can I pay with Visa, MasterCard or Amex for all currencies?
Yes, Visa and MasterCard are accepted for all currencies available on www.fireflyz.com.my. Amex, Maybank 2U, CIMB clicks can be accepted for MYR transaction only.

I actually made sure the currency was MYR.

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This post has been edited by yeeck: Aug 10 2014, 02:09 AM