HALO: Master Chief Collection problem with HDR only

Afternoon folks. Still early days for me playing with the HDR features of Special K. Managed to get it working for a few games now but hit a weird issue with HALO MCC (Gamepass version).

I can get the game to hook with Special K and then select the HDR widget and choose HDR, which then prompts to restart the game like usual.

However, when I restart the game after enabling HDR it will not load up properly - it just continues to show my desktop yet I can hear the game has loaded in the background, and the mouse cursor changes to how it is in the Halo menu! It’s like my display (LG OLED C8) won’t ‘flick’ over into the game.
Alt-tabbing does nothing and the only thing I can do is force quit out of the game.

EDIT/ UPDATE
The game will run fine with Special K in normal SDR mode and I’m using the latest 0.11.1 SpecialK DLL ‘preview’ files.
I then tried putting back the SpecialK32.dll and SpecialK64.dll files from v 0.11.0.50 and this solves the problem of not being able to see the game! HOWEVER, using these HDR has no effect. I change the sliders etc and there is no change.

Any ideas what could be causing this? I saw the Digital Foundry video feature showed HALO MCC HDR footage using the new 0.11.1 HDR features so it must/ should work, no?

I have the same problem and I think it’s related to fullscreen. Playing it borderless window works.

Borderless is better anyway.

Flip Model doesn’t work in fullscreen in all engines, and Flip Model is a pre-requisite for HDR.

Refer to step #2

Thanks folks, will give that a try later and report back

Works!
Totally loving this retrofit HDR feature by the way. Absolutely awesome.