Sound/volume button not working bur the sound is on

[AC Question]

All of a sudden the volume button is not functioning properly.
It will not change the volume while watching videos etc,
but when videos are not being watched, if its pushed to reduce the volume it will put the phone into vibrate mode, and then if its pushed up increase the volume it will turn the sound back on (for the phone, not fir videos).
The sound is on full constantly.
Previously when altering the volume a sound bar would appear on screen.
Any advice would be great.
Thanks rob

 

[spongy999]

This question is for a Samsung note 4