Why is the display not working but the external display works?

There could be a couple of reasons why your internal display isn’t working…. reason #1 …the display settings in your operating system are set to external display only…… or…. they are set to clone and external display is the only one you can see because the internal display screen is broken, or there could even be a problem with your video card. Usually, it is just a matter of going into the settings/display and setting the computer to display the internal screen. Sometimes you can even find the lcd display key on keyboard (ususally f5 or it will have an screen icon on it) hold down Function key Fn and the F5 or screen key and that will change the display… I will need more information to be of further assistance like operating system, version, etc… Hope this helps