Unable to play 4k hdr blu ray 0x91d70001

Hi guys i have just bought a dolby atmos sound bar but now the 4k blu ray says no hdr device.

The picture is much worse as minus hdr but the sound is very decent.

My set up is

tv 55 sony xe90

xbox one S

sony ht xf9000 dolby atmos virtual surround bar and sub woofer

+ 4k blu ray.

all cables 2.0 hdmi.

Any ideas why now it wont play 4k blu ray in HDR?

Of course, disabling HDR defeats the whole purpose of purchasing 4K HDR Blu-Rays.

...and 4k blu-rays. watched BvS and Deadpool this week w/ 4k hdr - stunning.

I am having the exact same problem. With HDR enabled, my 4K UHD version of the Revenant has stuttering and dropped frames. With HDR disabled, it plays flawlessly. Auto brightening is off, I don't have 50hz enabled (it's grayed out). I do have 24Hz enabled.
Disabling 24Hz, with HDR enabled, creates a washed out, almost colorless picture.

Also, I have tried two different brand new 4k UHD Blu-Ray Revenant discs (first one was exchanged at the store). My XBox Blu-Ray player plays standard Blu-Rays flawlessly, with HDR enabled, with no stuttering. So, it's not the player, and it's not the disc.
The problem occurs playing 4K UHD Blu-Rays, with HDR enabled. I also have the latest version of the app, and my Vizio P55-C1 firmware is up to date (it updates automatically).

Thanks for the quick reply. Can you tell me if support for 4K HDR Dolby Vision for the Blu Ray player is a recent firmware update? The reason I ask is that all the info and reviews I have read say that the Blu Ray player only supports 4K UHD and not 4K
HDR Dolby Vision. Thanks again.