Why does the new Oculus Rift not allow for VR preview in UE 4.9?

Hello!

Fairly new member here. Up to now I have been using the DK2 version of Oculus Rift, and recently have been able to test out my own games on the new official Oculur Rift. The thing is, I am not able to play them in VR preview and the already packaged games (.exe format) were also not being played in VR mode after enabling the “Alt + Enter”.

I am using UE 4.9, perhaps this is the problem? Is there a plug in that I need to use to play in VR mode in the new oculus rift?