Ariel, thank you so much for your feedback on the controls!
The build submitted didn't have the controls fully explained, so control info is split between the itch page and the in-game menu; not ideal, and definitely something we'll get corrected once the rating period is over!
The way shooting should work is holding the "B" button (assigned to keyboard letter "C") and then tapping the "A" button (assigned to the keyboard letter "X") rapidly. There's a small bar above the "( X ) Shoot" text that indicates how much time you have to shoot before the enemy in front of you gets to make a move. When you run out of shots (there's a 'shots remaining'/'total shots number' display in the bottom right) you hold the "B" button (again, "C" on the keyboard) and then press Up to reload. Reloading doesn't happen automatically since it's a player action that also gives an enemy the chance to move/attack.
If that explanation doesn't help, please feel free to let us know and we can check into bugs with the gun firing! Thanks again for your feedback, we love hearing the positives and negatives! Also, Dance Zombie Dance is really cute, wishing you well!! :D