Apple TV not playing HDR content on my external monitor.

Gonna be a weird one. So, I just got an HDR external monitor (AOC Q27G3XMN), and most of it works fine, except for HDR in Apple TV giving me same washed-out SDR look as the desktop. Now the issue isn't with the monitor. HDR games play fine, YouTube HDR video play fine. Just not Apple TV, and I can't understand why.