BTTF The Game: Sorry, This account is not authorized for this game

Contact steam support I would imagine.
Seems to be a wide ranging issue across many of the new bundle's games. None of the threads I checked had any replies.

give me ;)
sorry but try to giveaway

I activated it

Is the only Tell Tale Games that gives you problem?

try running steam (or the game itself) as an administrator, and if you are not on an administrator account, try to check parental controls on your system configuration.
hope this helps
cheers

the drm free copies seem to work fine from what I've heard of others with the problem