Why can't I change my macbook's backlight? So apparently I cannot modify my Macbook's backlight using the keyboard shortcut:



I'm pretty sure it will work again if I restart it. But I wonder what may cause this: is it perhaps an issue with my hardware, or just some OS glitch caused by something insignificant?

Macbook Pro Retina, 15" mid 2014. El Capitan 10.11.
You set it with the F5 and F6 keys, and it should not change after that, except for the setting SystemPreferences->Keyboard->Keyboard  "adjust keyboard brightness in low light".