Windows 10 Oculus 0.8 On Laptop Screen Is Black

I am testing VR in Unreal,on desktop it’s good to show the scene,but the view in Oculus DK2 is black on laptop.My laptop’s specifications are here:
Manufacturer:Razer Inc.
Version:Blade
CPU:Intel(R)Core™i7-4720HQ CPU @2.60GHz 2.60GHz
RAM:16.0GB
System:64bitOS,x64processor
Graphics Card:Intel(R) HD Graphics 4600
NVIDIA GeForce GTX 970M
And my system and Graphics Card Driver have been updated.Now the driver(0.8 Version) of Oculus can recognite my device,but the screen is black when press VR preview.Can you help me,I feel a little anxious about it,thank you!