The console command you are look for is “vr.bEnableStereo” - add a 1 afterwards for enable and 0 for disable.
The way I’ve got it set up in a project is on my “VR_Start” event, I first enable the HMD, then run the console command “vr.bEnableStereo 1” then possess the pawn, remove the menu widget and finally set the input mode to game only.
In this example I have 2 VR pawns with different input methods and a Non-VR Desktop pawn: Posses VR or Desktop Pawn posted by jkelly206 | blueprintUE | PasteBin For Unreal Engine 4
The “control switch” variable is my menu widget. All these events are bound on “begin play” after spawning the menu widget and adding it to the viewport.
Hope this helps. If you can’t get it working, upload your blueprint to https://blueprintue.com/ and I’ll take a look.