Hey Justin

Another thing to consider is that, by default, the Zoom window must be in
focus for the mute keyboard shortcut to work. A handy Zoom command to
memorise is Control + Alt + Shift, which brings the active Zoom meeting to
the front, no matter where you are. Do this first if you've been doing other
things and want to ensure Zoom is in focus.

Note that you can individually set Zoom's keyboard commands to be global
keyboard shortcuts, meaning that they will work from anywhere. I do have
mute/unmute set this way because I'm often reviewing documents etc and don't
want to move back and forth between applications. You can change these
options in the Keyboard Shortcuts area in Zoom's settings.

Note that I'm pretty sure you must be signed into a Zoom account to access
settings. Also, be careful when setting a keyboard shortcut to be global
because it may clash with keyboard commands from other applications when
Zoom is running. Choose wisely, and probably best to avoid changing these
options if you're unsure.

All the best!

Ben