I have found that if the bridge connected to the FMC and the aircraft sits long enough, the display is not shown in the Cockpit Master but is shown on the VC FMC.  The keys work but shutting down P3D or MSFS is the only way to fix it.  I had hoped the menu P would have helped but it does not.  Not sure if others have seen this but it has been a issue for a while.  I have it plugged directly in the USB 3 computer and a good power hub.  tried changing the USB cable.  anything else to try? 

Just received my CDU. The screen worked fine but if I were to start my flight cold and dark, the screen will be blank, not an issue if it is started in taxi mode.