Screen turn black after Splash page in Oculus Gear VR

Hi, I am new to Oculus. I imported OVR in my Unity project and use the OVRCameraRig on my scene. But the scene didn't get loaded when run in samsung S6. It always turns black. I had waited for a long time, over 5 mins. It still stays black. I run it in Unity editor, the scene works but its not in VR mode. The console shows below warnings:

Failed to create Oculus HMD.

Compositor failed to initialize.

Bad config or LibOVR not found. VR disabled.

Oculus HMD not present. VRSettings.enabled set to false.

I have searched about Oculus HMD, still confused about it and I thought HMD is for Rift. Do I need to install any runtime? I have tried both Oculus mobile sdk and Oculus Utilities for Unity, either one of them works. How can I solve this? Have been stuck on this for a week. Please help!

I have Unity v5.3.4p6, Oculus Utilities v1.6.0, OVRPlugin v1.3.2, SDK v0.0.0, use Mac, run it in Samsung galaxy S6.