VR.InputTracking class problem

I’m trying to use this code for a FPS in my VR project:

rotationX += VR.InputTracking.GetLocalRotation(VR.VRNode.Head).eulerAngles.y ;
rotationY += VR.InputTracking.GetLocalRotation(VR.VRNode.Head).eulerAngles.x ;
rotationY = Mathf.Clamp( rotationY, -maxLookAngleY, maxLookAngleY );
var xQuaternion : Quaternion= Quaternion.AngleAxis( rotationX, Vector3.up );
var yQuaternion : Quaternion= Quaternion.AngleAxis( rotationY, Vector3.left );
cameraTransform.rotation = Quaternion.Slerp( cameraTransform.rotation, nativeRotation * xQuaternion * yQuaternion, lookSmooth * ( Time.fixedDeltaTime * 50f ) );

But this is not working (in the Android build on the phone)
It is as no input present. It has no effect on camera turns. This code is working correctly with Mouse Input Axis.
Any idea?

Thanks to everybody…