activation code has already been used

Do you have the game downloaded? Are you launching it from within Origin? At what point exactly are you prompted for the code?

1) no , I bought the game client on the disk . I activated the game , but then removed . now I installed the game again , but can't activate . 2) run the game through the launcher . 3) press the play button , I am asked : " sign in with your EA account to activate the game Dragon age 2 on this computer . " , enter , press the "enter code" , the code is entered automatically , click the " send " . then write to me that the code was already activated .

I'm having this exact same issue

I am also having the same issue. I purchased my copy as a digital download via gamefly. I had a computer issue and had to reinstall the game and also get the "activation code has already been used" message.

Sorry to hear about your problem.  Unfortunately there's probably nothing anyone here can do for you.
The AHQ is for "player-to-player" technical self-help and game-play discussions.
We're all just fellow gamers, doin' the best we can...

You need "official" support from the EA Game Advisors.
They are the only ones who can do anything about accounts, product codes, game authorizations, etc.
You can reach them through the Help Center (link at the top-right of every page here on the AHQ.)
 
After getting to the Help Center and filling out the required information, (Product/Problem/Platform)
look for the "Contact Us" button, then the "Live Chat", "Call Me", or "Email" buttons.  
Not the AHQ "Ask Now" one.  (You've already done that.)

The options you see may vary depending on your region and the time-of-day.

If you select "Live Chat" be sure you have enough time to wait before being connected to someone.

I always plan for it to take an hour, and am pleasantly surprised when it's less.  😕mileyindifferent:
 
Good Luck!