Friend Is having Trouble Buying Gems With Gift Card

Hello hello! So this is my 1st time posting on the forums since I bought the game at launch so sorry if this is in the wrong area. Anyways, so my friend went to a Gas Station earlier today and bought a Visa Gift Card for $100. He's trying to buy gems with it so he can get the Living World episodes that he doesn't have. However, whenever he goes to purchase gems on the Trading Post, it gives him the error, "Payment Authorization Failed." The card is activated and he tried buying something with it on another website and it worked. he also checked the gift card on Visa's website and it does show that the card is working and has more than enough money to purchase the games. We both tried to figure out what was wrong but we don't know what the issue is with the card. Is there another issue that could be affecting the purchase not working?

Your friend can contact the Billing CS Team via the 'Support' link above/below and 'Submit a Ticket'.