Galaxy Note 4 Mute/Pause gestures (turn over or palm over screen) don't work.

[AC Question]

I have the Motions and Gestures feature for Mute/Pause turned "on" with the check boxes checked for Placing palm on screen and Turning phone over. On my S3 this worked like a charm regardless of whether the ringtone/notification sound was default to the phone or something I downloaded from elsewhere.

Why won't this work on my Galaxy Note 4?

Is there another setting somewhere that I've missed? Is it b/c I've downloaded some additional ringtones/notifications from Zedge and the motion/gesture only works on the Note 4 default sounds?