external display

I have an external display that I want to use as my primary display with my MacBook lid closed. I have the display connected to my MacBook with a usb-c to Display Port cable and the it works fine with the lid open.

When I close the lid, the primary desktop switches to the external display for a few seconds and then the display goes to sleep. If I press a key on the keyboard, it will wake with the primary desktop on the external monitor for a few seconds then the display will switch to no signal.

Is there something specific I have to do to use the external display with the MacBook lid closed?