Not able to enter in VR Play Mode

Hi, I build a scene with some basic entices. And imported Core VR Asset in my scene. Dragged the VRCameraRig in entity panel and enabled the CurrentVRCameraRig. But when i click on Enter VR icon on bottom right of Amazon sumerian is gives error that "Please make sure that your system is connected and turned on. Here I am using HTC Vive Device and it is working properly on other platforms Can you suggest me what I can do to resolve this?