This happened when my old project was created in UE v4.15, and I had converted it to UE v4.2.
The only solution I’ve found for this was to create a new VR project (Epic Launcher>Engine Version>Launch>New Project (tab)>Virtual Reality>Create Project). Now Go to the content folder of that new project, in windows: rename VirtualRealityBP to VirtualRealityBP_02 to your original content folder. Re-open your project and map. Rename the existing Motion Controller Pawn (in VirtualRealityBP) to “Motion Controller Pawn Old.” Drag and drop the new Motion Controller Pawn from VirtualRealityBP_02 to the Blueprints Folder of VirtualRealityBP>copy. This will rename the Motion Controller Pawn to “Motion Controller Pawn 2.” Drag this into your level. Go to MotionControllerPawn_2>details>Pawn>Auto Possess Player = Player 0 (to attach the controller to the camera, again). Leave the VirtualRealityBP_02 folder in your project’s content folder.
