I have a M4800 laptop hooked up to a Dell docking station, which I just connected to a new Dell U2717D monitor. I use a DP to DP cable for the connection. With the lid closed the signal is lost to the new monitor. Never happened to my old monitor, which was connect via HDMI. I have the settings set at "do nothing" when the laptop lid is closed with power cord plugged in. Can't seem to figure this out. I also take it to work where I use 2 monitors, and have no issue plugging it into the docking station there with the lid closed. It boots up to the screens. All the equipment is Dell. Any help would be appreciated.