Ah! Okay so Windows + HDR is a minefield. Windows 11 has a major overhaul of how HDR is handled but it's still not 'ideal'. My recommendation is to leave everything related to HDR in Windows off. SDR is better for desktop use. So if we want to watch an HDR movie what do we do? Well JRiver supports MadVR, with MadVR, the player itself can trigger the switch to HDR using the Nvidia API instead of the Windows one. This ends up being significantly more reliable IMO. The only caveat is launching an HDR movie in JRiver with MadVR is going to mess up the colors for any SDR material you watch after in the program, just exit JRiver and re-open before viewing SDR content.
One important note, if you're watching an HDR movie, and try to do desktop things, the colors will be weird. So if you're a multitasker, HDR > SDR tonemapping might be more suited for you.