Which PH315-52 version do you have?, there's a couple. The two i did see don't have Displayport.
Have you tried Hdmi? Your monitor supports 144Hz via Hdmi.
You're welcome. Yeah that's a common misinformed belief 😉, it's a manufacturer choice to allow Hdmi to achieve over 60.
Displayport should have worked though so not sure why unless there's something wrong with the cable.