SteamVR released a motion smoothing performance update, and since we updated to that, VR preview is greyed out in Unreal Editor. This happened overnight. Yesterday fine, today, update and no go.
In the output log, we can see the following:
LogHMD: Failed to initialize OpenVR with code 112
But I have no idea if that was there before yesterday, since we never searched the log for VR before…