Laptop to projector works fine using short HDMI cable but nothing on screen when using 20 meter cable

Solution
Yeah, either a bad cable, or you're getting signal loss/degradation with a run that long. Try lowering the output resolution of the laptop and see if that helps. You may also need an HDMI repeater or extender for a run that long.
Yeah, either a bad cable, or you're getting signal loss/degradation with a run that long. Try lowering the output resolution of the laptop and see if that helps. You may also need an HDMI repeater or extender for a run that long.
 
Solution