1) try from the terminal
Assuming the application launches and you can see the UI, proceed with the remaining steps
2) Press F6 to select the desired sound-card
3) Press F3 to ensure we are only exploring [Playback] settings
4) Use the right and left arrow keys to move to different items.
If the item volume indicator has a little box with "MM" or "0", try toggling the mute status with the "M" on the keyboard. If you do not hear audio from the speakers, then toggle the item again to put it back to its original state.