This could be for a variety of reasons:
a) because there is not enough balance on the card. If you want to buy something for more than the balance on the card, simply ask the cashier to take a certain amount from your gift card and pay the remaining balance another way.
b) It could also be because you need to activate your card first.
c) The wrong details are being input (if you are attempting an on-line transaction). You need to enter the name and address you assigned to the card at activation in the billing section.
d) The card may have expired, so please log on and check the status (see Note 3). If the card has expired, please complete the “Card Re-Issue form” found in the “Need Help” tab. Fees will apply.