PC Game Issues Activation Key / Redeem Code:

[penna-18]

I bought Assassin's Creed: Syndicate on ebay recently. And I entered my CD Key Activation Code:

And it reads as followed: "This CD Key or Activation Code is already in use with another Ubisoft Account. For more information, please contact Ubisoft Support (in red)."
How do I resolve this?

WHY are you allowed to sell a video game on ebay, if you are selling something that isn't playable. You can't play an already used video game, can you?

[mega-ma-roo]

If you can't play it, it is defective. See here for how to get a refund for defective items:

Return an item for a refund | eBay