Need Assistance with Sound Icon in toolbar so I can adjust the sound when needed

Can  anyone assist me with how to figure out why the sound icon stopped working?  I can no longer adjust sound on my Dell All-in-One.  It was working find since I hooked up the computer but tonight it suddenly stopped working.  I am trying to use it via touch screen monitory and have hit it at least 30 times but nothing.  The icon usually shows the )))) after the icon but none of those are showing since it stopped.

I'm a new Dell user and tried some sound suggestions I got in trying to research the answer myself but none of those were a fix.

Please reply back to me  if you can help me.  I need this working ASAP as I do need to adjust sound daily. (like when the phone rings) 

You can also email me as that may be the fastest way for me to get the answer I need.  Email address is .  Thanks bunches and have a great day!