Why won't steam accept my product activation key?

I tried activating my steam code to put Portal 2 on my computer, but when I did it said the key has already been used. I synced my psn account with steam but Portal 2 definitely is not showing up on my games list.

ps. I know for a fact that I synced my ps3 with the same account that I'm trying to activate the game with.

Additional details - May 11, 2012 7:28 am GMT

I originally bought it brand new with the shrink wrap on it.

Submitted Answers

From curtisalanmcgee on May 19, 2011 12:41 pm GMT

If you bought the game used, then that is why it doesn't work. Somebody already used the code.

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GameSpot Walkthrough

Portal 2 Walkthrough
Return to Aperture for further testing. Our Portal 2 Walkthrough provides a walkthrough for story mode, tips for co-op, and unlockables.
- Go to Online Walkthrough »

Walkthroughs & FAQs

Type	Name	File Size
FAQ/Walkthrough	FAQ/Walkthrough by anarcho_selmiak	152K
FAQ/Walkthrough	FAQ/Walkthrough by anarcho_selmiak	160K
FAQ/Walkthrough	FAQ/Walkthrough by redapocalypse04	93K
Other	Easter Egg Guide by jimmythesnowman	55K
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Spoiler-Free Walkthrough	Spoiler-Free Walkthrough by alerek	53K
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Achievement Guide	Achievement Guide by Dark Raven X	15K
Walkthrough	Walkthrough by Singspike	24K

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Portal 2

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Publisher(s): Valve Software
Genre: Action
Release: Apr 19, 2011 (US) »
ESRB: E10+

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