Hi. I more than double checked before leaving the comment. I have activated almost 7,000 keys so I believe that I am familiar with the process.

Step 1: Verify that I do not own this DLC. Steamgifts, ESGST, and Steam store all indicate that I do not.
Step 2: Activate a Product on Steam. Enter key (cut and paste). Receive the following message "Product Already Owned"
Step 3: Click Finish to begin Install of the game associated with this key. Receive this message "You are about to install Crazy Machines 2"
Step 4: Downloading Crazy Machines 2
Step 5: Views available Add-ons. Back to the shop addon is not owned.
Step 6: Steamgifts, ESGST, and Steam all indicate that this addon is not owned.

Unfortunately, I cannot mark this received. I continue to believe that this is for the base game Crazy Machines 2, which I already own.

I agree to delete my entry or the giveaway. If you prefer, you can also request a reroll and go through this with someone else.

kikuchiro's account, the other winner, does not show this DLC owned either. Some users make mistakes. I have seen many users get suspended from Steamgifts (temporarily for first offence) for not activating the gift identified in the link. I can refer you to this rule if needed.

Sometimes the activation fails and a user does not notice. Sometimes a completely different game is activated. I have seen many examples of stores selling keys but providing keys for a different game.

It might seem better for you if a winner mistakenly mark the game received, but the suspensions happen fairly quickly and regularly, so it is a short-term benefit, if any.

My suggestion for you is to verify that neither my account nor the other winner's owns this DLC. You may wish to notify the other winner of this mistake so that they do not find out by getting suspended. They may not be happy to find this out afterwards when they see that you have been told about it. It would be better to delete the giveaway and create one for the base game.

I'm sorry that this happened. It happens to all of us time to time. I hope that I have convinced you that I have made sufficient checks to conclude that this key is not for the DLC identified in the giveaway.

Best wishes.