This isn't a big deal because I don't watch a lot of HDR content, but I do notice I can't get the HDR badge on my screen when viewing HDR content with the Mi Box. My tv has a built in Roku so when I play the same 4k HDR movies from my Plex server on the TV's app it shows HDR. Playing that same movie on the Mi Box doesn't, it's the same for YouTube and Netflix.
Any settings I need to adjust on the Mi box?
Mi box can only do HDR10. It cant do Dolby Vision. Maybe that is your issue.