My friends volume isn't working

Here are a couple things to try/rule out.

-Turn the volume all the way up

-Try sound from multiple sources (YouTube, iTunes, Safari)

-Classic, turn it off and back on

-Make sure no external devices are connected and try sound again

-Update your version of macOS

-Restart the sound controller

-Open Activity Monitor-->fine coreaudiod--> select it and click the X to end the process--> Try sound again

-Check System Preferences

-Open System Preferences -->click Sound--> Click Output tab-->Click on Internal Speakers-->Make sure 'Mute' isn't selected and make sure the slider is moved to the right.

Hope this helps.

-Warren-