Can't add Orbital script - "The script needs to derive from MonoBehaviour!"

I am developing for the Microsoft HoloLens 1. I am trying to add the Orbital script from the Mixed Reality Tool Kit to a GameObject, but I keep getting this error message:> "Can't add script behaviour> ScreenSpaceMousePointer. The script> needs to derive from MonoBehaviour!" I don't understand why I'm getting this message, since I'm trying to add Orbital, not ScreenSpaceMousePointer, and I did not write the Orbital script - Microsoft did.