my volume on my iMac pro stop working i check the settings and is set on out put

Hi, dany148, maybe I can help you. If you have your audio/sound output set to anything other than Analog, eg non- digital speakers or headphones , Eg USB input/ output or digital input/output you will not hear anything. And the volume control will not work. Also if you pick a frequency your imac pro cannot reproduce or a bitrate it can’t handle, that could lead to no sound. You could run Audio MIDI Setup, in the Utilities Folder, to fix that. Also under System Preferences, then Sound, then alerts/effects, then play sound through: built in speakers or Line out should be available. Try picking one of those then try clicking on an alert/effect to play it. You should hear a sound, which means it’s working... if you hold down the ‘option’ key on the keyboard and click on the speaker icon, top right of your screen, it will show all available audio( sound) inputs and outputs. If that still doesn’t work , shut down your iMac Pro, restart, do a reset of the smc/pmu, followed by a deep reset of the pram. [hold down Apple/command key+option/alt key+p+r together for 4 chimes/bongs, then let go of those 4 keys and let rhe iMac start up as per usual]

good luck to you

John B