Function Keys of ASUS Note books not working has appeared in many threads on many forums.
I found those solutions worked earlier, but did not work this time!
The recent solutions have been:
1) Run C:\Program Files (x86)\ASUS\ATK Package\ATK Hotkey\HControl.exe
2) http://www.asus.com/support/Download/3/111/0/1/29/ and then restart
3) Update individual drivers (wi-fi, audio etce etc) or ATK Package or ATK Hotkey Utility etc.
When it did not work initially, a few years ago , loading / updating ATK Packge worked.
Recently, I ran an updated "cleaner" it stopped. 1 to 3 solutions did not work.
But with Running C:\Program Files\ASUS\Hotkey Service\HotkeyService.exe.
all the function keys have become alive.