When buying Funcards or any AP cards:
1. Make sure the person at the shop desk "activated the cards" and possibly get a receipt with the purchase to show the cards are activated.
2. Make sure you have clicked the right country/currency flag when you visit:
But since you are from the U.S. it should be already set for U.S. Dollar when you enter that page.
3. As stated by IBambi
Make sure your have entered the pin number on the correct text box.
If you have done all this then the only option would be to send a ticket, like Bambi said.
If the GM's say that your cards are not activated, then you will have to take your receipt to the place of purchase and take it up with them. Without a receipt, they still might possibly activate them, as they did for me long ago.