回复：power button was broken.

You PC gets its power from the power supply and the power supply is directly connected to the motherboard of your PC. But the power button of your PC actually controls the on/off of the power to your PC. The power button is connected to a wire which is then connected to the main board (motherboard) of your PC via a power switch connector. So the broken power button of your PC is at "off "position now, you have to get it fixed before your PC can get its "on/off" signal from the button.