Did you start the game from your steam library or from somewhere else (Desktop shortcut, FAF, etc.) ?
If you started it from Steam you are probably looking for a non-FAF mod that mods the Vanilla steam lobby to support 16 players. Can you remember where you found that "updated lobby"?
Or maybe you added the FAF version (non-steam) to your steam library as link, in which case you would have to install FAF first.