Dolby Vision not working at all and I don’t know why. I have a capable TV to support it. I...

But know that HDR and Dolby Vision are two different, incompatible, color schemes for UHD TV sets. Most support HDR but some support Dolby Vision. There are a couple of websites I check for this kind of tech talk but I don't think we csn post links to
outside sites here. Most UHD tvs support HDR 10 but I've heard Dolby Vision is better. Xbox One does not support Dolby Vision, just HDR 10.

OK,

I looked up the specs on your TV and it doesn't actually support HDR10, but rather Dolby Vision. Not all TV's support both options, some are one or the either, and in your case your TV supports Dolby Vision, which is actually better overall.

On your XBox, go to Settings ->General->TV & Display Options and under the SETUP section choose 4k TV Details. This will tell you what is detected by the XBox as being supported by the TV. Keep in mind, your receiver could limit what you're capable of if
the receiver itself doesn't support certain features.

I would say, connect the XBox directly to the TV, power up the XBox, and go into setting as listed above and see. You may just need to turn on Dolby Vision instead.

Vizio is working on a Firmware update for its TVs to support Dolby Vision. Microsoft uses a "low latency" version from Dolby, and TV manufacturers are scrambling to catch up. The full supported list is here:

https://www.windowscentral.com/full-list-tvs-support-dolby-vision-xbox-one

More will come, it just takes some time.

Yes, please bring Dolby Vision support to the Xbox 4k Blu-ray player! I have a vast collection of 4k Blu-Rays and a tv that supports Dolby Vision (LG C9).

Of course the Blu-Ray disks I'm using are UHD and have Dolby Vision.

Dolby Vision is enabled on Xbox One X settings, TV HDMI ports are in Enhanced mode (4:4:4 4K/UHD HDR 60Hz), and the TV test (that can be found inside Xbox menu) returns all green ticks for my Xbox-to-TV connection.

As said, Dolby Vision works with all streaming apps... but not when playing Blu-Ray UHD Dolby Vision disks.