No sound or unable to unmute speakers

Info:

This happenned to me one time when I booted my computer. No matter what I did, my speakers were muted and I was unable to mute it from GUI in the Pulse Audio Controller app.

Solution:

• Open your terminal.
• Type alsamixer which is a CLI tool for audio.
• Once the app is open, press m key of your keyboard to unmute your speakers.

This should unmute your speakers. This happenned to me once I had a problem with the speakers, and I resolved it this way. So you can try it.

For more info, you can check, Arch Wiki's, Pulse Audio Troubleshooting section. I found this solution from there.