Touch Key Light setting not appearing on display nor in all settings on SM-G925I

[AC Question]

when i bought the S6 edge on lollipop it was fully functioning, meaning, the capacitive buttons are lighting up and settings for those were displayed in the Display Setting. But when I started updating it to Marshmallow it went wrong and all of a sudden the capacitive buttons aren't lighting even when I'm not in power saving mode. Hoping that I would fix the problem and new Nougat update is rolling I installed the update and then, nothing has changed. How can I fix this problem?