I figured it out. I was having the same problem. Is your power saving mode on? I turn mine on when I got it, then later realized my buttons weren't lighting up either. Just found out it was because of having the power saving mode on. Hope that helps!
U SIR, U ARE A GENIUS
I WAS BLAMING MY SELLER FOR THAT, LIKE "YO U SELL ME A DAMN PHONE ALREADY WITH BUTTONS NOT WORKING, GET UR **** TOGETHER AND FIND OUT A SOLUTION".
And i had the battery saving on, shame on me, honor to you <3
i bought a galaxy s3 off a friend and the back button and the menu button don't light up or work. i have tried everything the power saving mode is off and i put that one setting to always on.. my friend said it always worked for her but i don't know will somebody please give me ideas of what to do.. the top notification led light works i dont know why the bottom buttons don't light up I've tried everything
Having this same issue with both my phone and my tablet. Both got an update recently. Update changed and broke some of my setting features. I tried turning off power save did not work.