My Vanilla Visa Gift Card won't work online ?

I already went to the vanillavisa website and registered it i think like i went and it only asked for my zipcode . So i gave it , then i go to forever21.com and go to place my order and i type everything in then it showed this "We are unable to place your order at this time. Please call Customer Service at 1-888-494-EVER for further assistance." What does this mean how do i get it to work ? Did i not register right or do they not work online ....