Built-in display not working

Hi I installed openSuse while my laptop was plugged into my external monitor. After the installation I tried to start my laptop without the external monitor, but then i just get a black (blank) screen. After connecting the external monitor I've set the display settings to mirror, but this still doesn't work. Anyone any idea how to solve this problem? Do I need to install again while not using my external monitor?

Thanks for the help in advance!