Did you enable HDR on your HDMI ports?
"take a trip to picture/expert settings/HDMI UHD color. In this option, bizarrely, you actually need to manually enable HDR support for each of the HDMI ports on the screen (the KS7000 has four, but mileage will vary depending on the display)."
Then you have to restart your console and enable HDR in the PS4 video settings