CD Key Already Redeemed

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i Bought Blacks ops 3 on disc a Couple years ago now and when i first got it i tried to download it i didn't know anything about computers and i had 2 drives one was full and i didn't know i could download load it(i tried to and redeemed the code) when i remembered i had the game and tried to install it again it said the CD key was already redeemed to my account(it's not in my library) and i could email myself to figure something out

[cSg|mc-Hotsauce]

Go here... https://help.steampowered.com/en/wizard/HelpWithGameIssue/?appid=311210&issueid=101