I've recently been having issues with my monitor. Laptop starts up, runs fine. Nothing is shown on the monitor(black lit screen) but can be seen on an external monitor. Laptop monitor shows the screen with lock, switch user, sign out, and task manager, when I push ctrl+alt+delete. it also shows a grey screen when stating "shutting down" or "restarting." those are the only time my screen is working. What should I do?