You replaced broken LCD screen but the new screen is not working

You replaced the broken LCD screen in your laptop with a new screen but it’s not working. Does this sound like your problem? Let’s find out what could be wrong and how you can fix it.
First of all, I assume that your new LCD screen is compatible with the old one. Different screens require different video cables. Make sure you new screen is compatible with your laptop.
OK, let’s say you accidentally damaged the LCD screen in your laptop. A part of the screen still works fine but you cannot use it like that so you decided to replace the screen yourself. You can find LCD replacement instructions in service manuals or this DIY site.

You did some research and purchased a compatible screen, installed it into the laptop, turned it on and… The new screen is not working!!! What could be wrong?