When trying to redeem Humble Bundle gives a greyed-out message stating "Keys are temporarily exhausted for this product". Tried a few times over the last few days and same message.

In my experience, all of the games I have on Humble that have ever given this message have never been refilled, so I'm not sure if/when this will ever be redeemable. You might need to contact SteamGifts mods to resolve this giveaway.