Try unistalling SDK by going to Play games in steam, right click SDK goto properties. Click delete local game content. Then re-download it through steam and it should get all the files again, thus fixing your problem. Good Luck
Sometimes this occurs when you haven't updated, restarted, or connected to Steam recently. (Recently is a fairly relative term, which can be from minutes to days.) Try right-clicking the Steam icon in your system tray and shutting it down, restart it and make certain you are connected to the internet so that it can update/check your account status, then try running your map.