Unfortunately these codes were among those that we recently discovered to have been purchased fraudulently. We have canceled the codes and, most importantly, issued refunds to the owners of the stolen cards.
I would strongly suggest that you contact whomever you purchased these codes from, and demand a full refund.
I apologize for any inconvenience caused.

On a side note, it's worth pointing out that selling GOG gift codes is forbidden as per our User Agreement (3.3) so these should never have been put on sale anyway.

Buyers of these codes usually don't know if they were purchased legally, so your friends are not at fault. They should demand full refunds themselves, though. I'm sorry to see that this situation turned out so complicated, but in this situation there is nothing else that we can do. Giving the money back to whomever had their card info stolen is the top priority.
I hope this works out well for you, and you will get your money back in the end.