I had Unity 5.6.3p1 installed fine and working and building fine. I then installed Facebook Gameroom support, and now I can't build anything for Windows Standalone, I get a bunch of these errors all over my project... error CS0234: The type or namespace name `SceneManagement' does not exist in the namespace `UnityEngine'. Are you missing an assembly reference? as well as errors like... error CS0246: The type or namespace name `Sprite' could not be found. Are you missing an assembly reference? error CS0246: The type or namespace name `Color' could not be found. Are you missing an assembly reference? Its telling me UnityEngine.Color or UnityEngine.Sprite don't exist. Why does installing Gameroom support cause all these issues, when I'm not even building for Gameroom? I also uninstalled Unity and installed everything from scratch, and I still have the same problems. EDIT : Confirmed, when I re-install Unity without Gameroom support, I can build to Standalone again fine.