You are receiving this reply because you categorized your ticket under CD Key questions > Duplicate CD Key issues.
Many CD Key issues can be resolved with this first response. We encourage you to read the information below and reply if you need further assistance.
The “Duplicate CD Key” message you are receiving indicates the CD Key has been previously registered to and played by another Steam account. If you have recently purchased this product, please contact the seller to discuss a refund or exchange.
Used CD Keys cannot be activated via Steam. This includes used CD Keys received as gifts, resold by an individual, or purchased from a store selling new or used goods.
If the duplicate key you have belongs to an account you previously created, please hand write the ticket number on the CD Key and submit the image in your reply. We may be able to use this information to help you gain access to your old account.
Steam Support is not able to move keys between accounts or remove keys from an account so they can be activated again. Additionally, we cannot provide information related to the original registration date of duplicate keys.
Duplicate CD Key issues for games that require third party logins (Games for Windows Live, Uplay, Rockstar Social Club, etc.) must be resolved by the game’s support department. We have no insight into these third party accounts and cannot make changes to these accounts and the CD Keys associated with them.
We apologize for any inconvenience and appreciate your understanding.