We've had this issue intermittently for the past 18 months or so:
On occasion, but not all the time, Revit is started up, the file is opened, Enscape is started, but the SpaceMouse does not respond in Enscape. The SpaceMouse side buttons do function and indicate that it is configured for use in Revit. Sometimes, if the Revit window is made focus again, and the user clicks a mouse in the Revit window and wiggles the SpaceMouse knob just for superstition's sake, then refocuses on the Enscape window and clicks, the SpaceMouse will begin to respond in Enscape. This behavior has only been observed with the SpaceMouse wireless.
Currently the machine is running:
The same behavior has occurred with Revit 2017, 2018, and 2019, Enscape release and preview versions going back over a year, and 3DxWare 10.5 and 10.6.
Checking some forums today I saw that Revit uses the SpaceMouse differently for 2D vs 3D views. Could it be something to do with which type of view is open in Revit when Enscape is opened?
Has anyone else seen this? Any suggestions on sequence of startup or which window to click in to get the SpaceMouse to control Enscape?