Only other thing I could suggest is maybe try re-installing the Steam client, and see if that helps in anyway.me neither mate, I've never seen that screen I posted up the page before.
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Ah I see. That explains it then. Saved a return trip to Game then. But this one has got me baffled tbh. Never come across this one beforeIt's because they can't check if the activation code has been used. They won't replace it, because people would just go in and say it wasn't working and get a new one all the time. You will have to contact SI or Steam.