P2418HT - Touch not working unless set as Main Display?

I have a Touch Screen monitor that works well as long as it is set in Win10 as the Main Display when extended from a laptop. I have a need/reason that I need to make the laptop the main display. When I make this change, the Dell P2418HT still has touch enabled, but the touch controls the display of the laptop, rather than the extended screen on the dell monitor. 

Is there a configuration or something that needs to be changed to ensure the dell monitor touch can react to whatever is on its own screen, without having to set it as Main?