Mixamp Pro TR not showing up on Xbox One

I have a Mixamp Pro TR connected to my Xbox One. I wanted to replace my old Mixamp, so that I would not need a headset cable to the controller anymore. Both the Xbox and the Mixamp Pro TR are updated to the latest firmware. The Mixamp is connected to the Xbox with the USB cable and the optical cable. My old A40 headset is connected with the Mixamp. Also, the Mixamp is in console mode (red ring).

When I go into the devices settings menu of the Xbox, I only see the controller, but no "Headset"...

Mixamp Pro TR not showing up on Xbox One