MacBook Pro Keyboard Backlight not working

ewfarquhar wrote:

The backlight on my MacBook Pro keyboard is no longer working once I log into my user account. The keyboard does light during boot up, so I know the lights physically work. After logging in, the backlights never come on again. I have reset SMC, created new user accounts, deleted user accounts, reformatted SDD and reinstalled Big Sur, both without importing from backup and with importing the backup. I have even taken it to the Genius Bar where it passed all hardware tests and they also reformatted and installed Big Sur. I'm at a loss. I do not believe this is a hardware issue, so I was not willing to pay the $400+ fee to replace any of the hardware. I'm 100% convinced it's some kind of software problem, but I'm at a loss as to what it could be. What else could it be?

>System Preferences>Keyboard

make changes to test then come back to your preferred.

If the ambient room light is strong it will automatically turn off the back light, you test this by covering the light sensor next to the facetime camera.

Try resetting the SMC https://support.apple.com/en-us/HT201295

Try resetting NVRAM/PRAM http://support.apple.com/kb/ht1379

Turn your Mac keyboard's backlighting on or off - Apple Support

ewfarquhar wrote:

I have already reset smc and nvram/pram. There is also no setting in keyboard preferences for keyboard lighting.

You can always reinstall the macOS on top of your existing macOS to sort anomalies, if you still have the issue:

How to reinstall macOS from macOS Recovery - https://support.apple.com/en-us/HT204904

Another similiar situation with backlit keyboard found a few matches

in this duckduckgo search result page; some were adequate. Others

seemed to be filler. (I avoid those which say [Ad] next to their URL)

This has a few good ideas on how to try and set backlit keyboards:

https://duckduckgo.com/?q=how+to+control+keyboard+backlight+in+macbook+pro+2020&t=ffab&ia=web

https://duckduckgo.com/?t=ffab&q=how+to+control+keyboard+backlight+in+macbook+air+2020&ia=web

Although my choices are usually very cautiously approached; I'm

also careful when browsing the web; to avoid adware + malware.