While the system is off, press and hold the power button. It will beep once, and while you continue to hold it, it will beep a second time. Release it when it beeps the second time.
This should detect the correct resolution and change it.
While the system is off, press and hold the power button. It will beep once, and while you continue to hold it, it will beep a second time. Release it when it beeps the second time.
This should detect the correct resolution and change it.