As I found out just yesterday, make sure the adjust refresh rate option is set to Always or On start / stop.
Might wanna try LG’s UHD 60 FPS HDR demo. Also experiment if the HDR autoswitch option of the Vero does anything for you.
When starting to play HDR content, my LG B6 displays a small popup bubble that even says HDR. You can also point in the upper left corner with the remote and click to display the current content’s specs.