If you have a dell xps series pc, may be you faced with the same problem;

1- Sound controls not working

2- Keyboard brightness controls not working etc.

Please check before you search the problem and download any driver etc. 🙂 it may be very simple. There is a”fn” lock in your “Esc” key and you just need to press fn and esc together to unlock the “fn” key. Thats very simple.