I am trying to fix the sound on my Apple Mac book. I have adjusted my sound volume but cannot deselect mute. How do I deselect?

Hard to say what may 'just work.' However you could try reset

of System Management Controller. ~ Follow all details as they

may apply, (or may not, to your specific model.)

• How to reset the SMC of your Mac - Apple Support

https://support.apple.com/en-us/HT201295

Some other resets could help; conditionally.

• Reset NVRAM or PRAM on your Mac - Apple Support

https://support.apple.com/en-us/HT204063

• How to use Safe mode on your Mac - Apple Support

https://support.apple.com/en-us/HT201262

..Sometimes the simple process of 'shut down, & start up

in Safe mode' ~ per article instruction, can help fix stuff..

Then restart again to run Mac in normal mode.

(Note: articles which apply to both Intel-based Mac -&-

Apple Silicon-based Mac; may require additional detail.)