I’ve followed the setup for it. Now, the preview is working, it was minimizing the engine and once I maximized it again the preview worked.
I think I’ve found the problem with the packaged/cooked version. For some reason it isn’t doing fullscreen properly. A border is overlapping onto the desktop monitor, coming from the HMD monitor. If I make compositor fullscreen it does nothing, but if I click the game icon, the game takes control, but overlaps so I get red eyes. I think its a resolution setting, so maybe running it in a window would work. I’m not sure how to set that up, though.
edit: the VR preview has the same sort of window overlap onto the desktop monitor, so I don’t think that is the case.