Hello there,
I have the same problem, after some windows update my keyboard lightning is not working anymore. It stays off, the buttons ( FN + arrow up / down shows me the menu ) but even if i get them to max brightness is not working.
I have a ROG Zephyrus G14 / Windows 10 Pro Version 20H2 Build 19042.1110
Please let me know if you have any fixes for this.