Good evening !
I own a galaxy s7 (g930f) with the latest stock android available for it (android 7.0). The problem is that the recents button both works and lights up properly. However, the back key works properly but doesn't light up at all. I am aware of the power saving disable of lighting up. Also, I tried restarting the phone and the problem still persists. Furthermore, I even tried to install Galaxy Button Lights 2 to try to reset the lighting up settings. Also, I recently changed my battery alone and everything went smooth, I didn't encounter any problems myself, considering the BACK button is still functioning but it doesn't light up. I usually keep the phone in power saving and I just noticed today that this happens, so I can't exactly tell since when. Please tell me what I can do. Any help is appreciated. Thank you in advance !
It's possible something was disturbed within the phone when you replaced the battery yourself @luciyanmihai
Unfortunately as you now have voided any remaining manufacturing warranty Samsung most probably wouldn't service the phone.
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I have no affiliation with Samsung.