If it uses a A/C power adapter aka (power brick) that the first thing I would check.. if you have voltmeter you check the voltage to make sure it's at least rated at or above the sticker value, if not try replacing it. If it uses a standard computer power cord and the power supplies is built-in to the monitor it might be bad or the main board has gone bad. Those most common cause in the that order power supply or mainboard.