Ok, it seems that I misunderstood.
According to administrator you mean that the code did not work, is that correct?

If that is the case it would be weird, I revealed the key from HumbleBundle about 5 seconds before creating giveaway so I doubt anyone had the chance to use it.
Also it does not seem like I added incorrect key by mistake.

If this code does not work, please choose other key from list below instead:
(please note that duplicate happened on two of my givaways so I am presenting this list there too, in case of a conflict first one gets the key ;) )

Verdun
Divide By Sheep
Primal Carnage: Extinction
Battlerite DLC: YogYog Bear Mount
Binary Domain
The Blue Flamingo
Crusaders of the Lost Idols Legendary Starter Pack
Spectrum
Team Fortress 2 badges - Mandrew's Munificent Mug and Israphel's Eleemosynary Expression
Teslagrad
Toy Odyssey: The Lost and Found
War for the Overworld - Yogscast Worker Skin
Zero Reflex: Black Eye Edition
Grey Goo Definitive Edition
Satellite Reign
The Warlock of Firetop Mountain
Dungeon Souls
Samorost 3