I have no sound output in the rift headphone either in home, or in VR games when I set the output device to Rift Headphones or Audio Mirroring.
Before I was using my own headphones with the rift and that was working fine but I decided I was going to try the rift headphone for the sake of convenience.
I know it's a software issues since I CAN make them them work sometimes by restarting the OVR service and home several times. And also if I set my windows default audio output to the rift headphones and play music for example, the rift headphones works. So, it's definitely not a hardware issue.