Card that won’t work

I bought a $500 card for a friend. He said it wouldn’t work. Later I found out the my credit card kept it pending for several days. He gave it back to me so I sent it to a company that buys cards to try to get part of my money back. They notified me the card still had $500 on it but their machine marked it as fraudulent. They are going to send the card and receipt back. The card was never used. How could it be fraudulent ? Can I get my money back? I don’t know what was wrong with it but I lost $500. The stores won’t exchange any cards. I feel that apple should refund my money.