My 2016 AW 17 R4's touchpad backlight is not currently working.

I once fixed it by changing the BIOS setting for touch backlight to ON from AUTO. But today that does not seem to work. I went to ON, then AUTO, then back to ON, rebooting in between, and none seem to work.

My keyboard backlight works but not the touchpad.

What next steps should I try? Full BIOS "Load Defaults"?

Thanks for any advice,
Nick