If you did not register the card, the website won't allow it if the balance is $0.00 so you have to do it by phone before filing the dispute form.
Did this happen to anyone more than 30 days ago? Some prepaid cards hold temporary authorizations for 30 days. I was affected on October 13 so I will be filing for a $500 loss. The charge immediately appeared in the same manner as a posted charge. I am not sure whether the
https://mcgift.giftcardmall.com website actually has a different way of displaying temporary authorizations vs. posted charges?
The dispute must be filed within 60 days of the purchase, but the instructions say "a merchant has 30 days from the date of return to post a credit to your card account."
Unfortunately they will probably just rule against everyone.