Make sure the power cord is connected and the power switch on the back of the projector is turned on. Then wait a moment for the power button to light up before pressing the power button on the projector or the On button on the remote control.
If you've set the Control Panel Lock, the control panel buttons are disabled except the power button; you must use the remote control to turn on the projector. To disable Control Panel Lock, press and hold the Enter button on the projector’s control panel for at least 7 seconds. See Locking the Projector.
If you've set the Child Lock, you have to press the power button on the projector for 3 seconds to turn on the projector, or use the remote control. See Locking the Projector.