Won't turn on! No green light to show that it has turned on.

How to replace the lamp in your Mitsubishi TV
In an another youtube, it was clearly told that the outer cover needs to in place perhaps to engage an internal switch

Look for a tiny hole in the button panel. It may or not be marked reset. Straighten out a paper clip and push it in the hole slowly until you feel it stop. Gently push it to reset the TV. If that doesn't work, then look at the lamp cover door to see if it is closed all the way. The switch may be bad too.