Nvidia NVS510 and Display Port

Hi

I have the Nvidia NVS510 and using a displayport, it does not register the Nvidia card in Photoshop, it's defaulting back to the integrated GPU.

However, when I switch from Display Port plug - and plug it in using a Mini-HDMI - HDMI adapter it works fine (mini-hdmi from PC to HDMI socket on monitor).

It won't work when standard HDMI cable either.

Any ideas on how to get it to work with the DisplayPort cable???