I got my Amex Delta Skymiles Gold card the other day and have begun faithfully using it for the SUB, and I ran into a roadblock trying to use it for renewing my once a month DC Metro Smartcard. The Smartcard website would not take my Amex for anything. I called Amex, and they said that I should be good to do. I can't believe the CSR never mentioned this issue.
I've never had an Amex card before and after researching I found out for online transactions with Amex you have to use the 4 digit PIN on the front of the card rather than the 3 digit CVV on the back! What?!? Haha, anyway, it's all good now, but I thought that was crazy. SUB here I come! 
RobertJ ... appreciate your dillema! Ran into the same challenges and had no idea about the four or three digit codes. Figured it out by accident as no one told me. 
The part that kills me is the CSR had me on the phone and knew I was having trouble and never breathed a word of it. LOL...oh well.
@Anonymous wrote:RobertJ ... appreciate your dillema! Ran into the same challenges and had no idea about the four or three digit codes. Figured it out by accident as no one told me.
That is good to know and thank you!
@wasCB14 wrote:The three digit number on the back is used for confirming your identity with Amex sometimes. For example, on MR cards, both the 3 and 4 digit numbers are needed to link frequent flyer programs to an MR account.
Almost every web site I have seen that requires a CVV has something like this.
The four-digit number printed on the front of American Express cards is the CCID or Credit Card Identification Number. The CVV or Credit Verification Value is the three-digit code printed on the back of the card, on or near the signature panel. The CCID is an additional layer of security for the card. Amex Customer Service Professionals will usually ask for the CCID if you call them about a card-related transaction.
@Anonymous wrote:RobertJ ... appreciate your dillema! Ran into the same challenges and had no idea about the four or three digit codes. Figured it out by accident as no one told me.
What???
Well, that's how I finally found it, but as I've never had an Amex card I had no idea it would be any different. So I never bothered to even look. But ya...I saw that.
@longtimelurker wrote:Almost every web site I have seen that requires a CVV has something like this.