1.it can be the power switch is faulty 2.the battery/charging system may have failed or drained the power and need to be boasted to a charge that can power on the phone 3.the last resort is the motherboard is faulty Solition 1.Try connecting it to the charge 2.Disconnect the battery and reconnect then try powering on 3.if you have a voltmeter get the voltage of the battery should be around ~ 2.82V

Either the laptop have short circuit problem or bios problem need flashing