Have you placed a VR camera in your scene? Imported Oculus Utilities? Enabled the appropriate XR function in Unity? Made sure you're using supported materials? That your scene is lit properly? That your app scene is the scene you include in your build (and not some blank sample scene)? *Catches breath*
I had this issue, too, when creating a new project with Unity 2018.1 and Oculus Integration 1.34.0. However, I then created a new project with Unity 2018.3 (still Oculus Integration 1.34.0) and it worked as expected.