No HDMI output on Xbox one x

You don't need HMDI 2.1 for 4k on the Series X...you only need HDMI 2.1 to run at 4k 120Hz. The Xbox One X only ran on HDMI 2.0 but it output 4k perfectly fine.

My Xbox One X has the same issue. I only noticed it doing it recently. I usually have HDMI audio set to output bitstream (DD), but on startup I will occasionally see it has change the HDMI audio output to 5.1 uncompressed. It's easy to notices as my
receiver will show as outputting Pro Logic II instead of DD 5.1 as it should when the Xbox One X is outputting a bitstream signal over the HDMI.

A power cycle does nothing. The only way to fix it is to go back into the audio setting and change it back to output bitstream over HDMI. It also doesn't do it every time the system is turned on. Sometimes it will turn on and remain on bitstream output as it
should.

Strangely enough I just noticed it doing this since i got a PS4 Pro. Almost as if going from the PS4 Pro's HDMI input to the Xbox One X's HDMI messes things up somehow. Though I haven't been able to find a situation where that can be replicated.

In any case....it seems ludicrous that a setting like that will just keep changing itself.

So are you saying you plugged your cable box into the HDMI passthrough on the One X?

If the cable box is defaulting to a lower resolution when connected into the Xbox One X's HDMI passthrough, you should be able to adjust the display output in the cable box's settings menu.

I recently bought an XBOX One X and it worked fine for the first 6 months. I turned it on last week and the HDMI output is not working anymore.

You need a Xbox One-S or X for 4k(UHD)

You also might need to change the settings from you're TV for the HDMI output