A:Answer It happened to me after about 3 months of usage.
It was quite bad because the keyboard won't respond even after reboot.
here it is a possible fix that worked for me:
use the screen keyboard if possible to log in.
from another PC send an email to yourself with asus url: https://www.asus.com/us/Laptops/ROG-Strix-G/HelpDesk_Download/
Open the url, and under the drivers & tools select G531GT model, 64 bit Windows
At the bottom you will see the hot fix ROG Keyboard Firmware Update tool V2.1.8
download it, install it and reboot
It is a shame that such a critical defect was inflicted upon unsuspected consumers, and the fix is so convoluted.