Games isn't giveaway-able

It's been free before, thus cannot be given away.

May I ask?
Did You buy those game?

Shadow Warrior 2 dlc?
Sometimes if a game is pretty new and not actually released, yet, SG can't identify these games and thus they won't show up in the giveaways window. This could be particular be true in the case of a DLC. Though normally upon release they become available.

However, if a certain dlc or game isn't giftable and you are sure it was never free before, you can file a ticket and ask support to add the dlc or game to the giveaway list.