hi,
this may sound far fetched... hook up an external monitor and press Fn + F5 again, if it toggles to and from both screens.
if it does not work, try repairing Windows or reinstalling the hotkey drivers (F keys are part of the hotkey drivers, i think).
this may sound far fetched... hook up an external monitor and press Fn + F5 again, if it toggles to and from both screens.
if it does not work, try repairing Windows or reinstalling the hotkey drivers (F keys are part of the hotkey drivers, i think).