Q: why isn't my backlit keyboard not lighting up

Go to System preferences/Keyboard and check the settings there. You may need to press the fn key and F6 key simultaneously to bring up the light on your keyboard. More info at http://support.apple.com/kb/HT4882

1. Go to System Preferences > Keyboard

2. Uncheck the "Adjust keyboard brightness in low light

That solved it for me.

if the other options don't work, try resetting pram/nvram

i couldn't figure out how to fix my keyboard lighting forever! the fn & f6 simultaneously fixed it!!!! so so happy thanks again!

You're very welcome!

spot on.

Thanks that was a real lifer saver for me tonight!

That worked for me too!  Thanks!