Unplug your headphones and try connecting them to another device like your iPhone or iPad to make sure they are working as intended. Test them on any audio jack ports that you have on your MAC or other devices such as a PC or Smartphone.
Check the headphone jack for issues. Dust or fluff is enough to block the port from recognizing your headphones or speakers. Try blowing the dust off the jack and from inside the port on your Mac to see if that solves the problem.
Plug the headphones back in while holding the volume buttons at the same time.
Check the volume controls on your headphones, to see if the Mute button isn’t turned on or the sound volume lowered to minimum.
Check all the ports by disconnecting everything plugged into your Mac. That includes HDMI, Thunderbolt, and USB devices.
Other devices could be channelling the sound away from your headphones. If your TV is connected via HDMI, for example, your sound is probably being redirected to the TV instead of the headphones.
Should you want the sound to play through your headphones while your TV is on, you need to switch to your headphones by clicking on the audio icon found in the Mac menu bar.
Restart your MAC for effects to take hold.
You can also restart your sound controller by opening the “Activity Monitor” and locating “coreaudiod” in the process list. Terminate the process by clicking on the “X,” and it will restart automatically.
Try updating your macOS.
We would also suggest that you check out your Audio Output settings on MAC.
Open the Apple menu and select “System Preferences.”
Click on “Output.”
Choose “Headphones” as your output device.
Check to ensure the “Mute” box is unchecked.
Adjust the sound to your preference.
When multiple devices are connected to your Mac, your computer might try to play audio through the wrong device.
By manually selecting your audio output device, you should be able to resolve this issue in many instances.