Volume on Mac
How do I fix my volume on my Mac if it isn't working?
MacBook Pro 13″, macOS 10.12
First of all, try rebooting the device. Secondly, check for water damage on your speakers. Thirdly, try plugging in any third party speaker to make sure it is a physical problem with the device. Other than this, make sure you are on the latest software, and have no other tabs open.
Hope this helps!