Laptop will not display on external monitor.

I have a HP Envy 360 and am having difficulty getting the external monitor to connect to my PC. If I boot the PC with the monitor connected the display will load to the external display but my laptop will go blank. The only way to get the monitor on my laptop to work will be to close the PC and open it again with the external monitor disconnected. If I boot the PC without the monitor connected the external monitor will not display. I have checked the screen resolution settings and it does not appear to detect the monitor that is not connected. I have attempted FN + F8, this does not resolve the issue. Any ideas on what could be causing this?

Thank you.