This has been said before, but for those unaware, if you can't complete the tf2 quest on AWA is due to a change that valve did recently regarding free to play game licenses, similar to the Dota 2 issues. You have to be a premium tf2 user, you can purchase a Tour of Duty ticket in-game (that you can later resell on steam market) to acquire premium. If you're wondering why you could do the quest without doing that, it's because its also granted by purchasing The Orange Box or Valve Complete Pack on Steam.