AT&T GS 6 Android 6.0.1 no System Tuner UI

[AC Question]

Tried steps given somewhere else, 1) enabled Developer setting mode, 2) long press Setting gear icon in notification bar -- nothing happened and I still do not see System Tuner UI. What could be wrong?

 

[Javier P]

Welcome to the forums. As far as I know Samsung didn't include the UI tuner in their Marshmallow update. Sorry, there's no much you can do about this.