Unable to adjust the screens brightness
I have a Mid 2011 iMac Model: MD063LL/A that will not allow me to adjust screen brightness,
I've tried using the function keys on the keyboard, as well as in system preferences, the bar moves as if the screen is adjusting but the screen remains at full brightness.
The screen two days ago was at low brightness and would not let me turn it up, and after a reboot, and waiting a couple hours it magically came back to full brightness.
Any idea what can be the cause of this?
Computer is fully updated as well.