An Xbox One update recently introduced a new display bug. It can occur upon start-up or after switching between apps on your device.
If your video signal drops, displaying only a black screen while you can still hear audio, you may be affected by this.
To fix this issue, you have to perform a full shutdown. Hold down the power button for 10 seconds, then turn the Xbox One back on. It should displays as normal. If not, power it down and unplug all wires, wait a few minutes and turn it back on.