I figured out what the problem was. In that level, level 5, if you have the other extension turned on, you can't fire bullets. I just finished the game. That Was Awesome! The final boss was amazing. The only thing that I would reccomend is allowing the player to die in the final boss fight, so that there are actually stakes involved. But either way, I loved the game. I will absolutely be leaving a positive rating and review. I think that this has potential to become a full game. Great work, and congratulations on such a great release.
I submitted a game for the Game Maker's Toolkit game jam about a month ago. I know it's not great, but if you could play it and give me your honest opinion, it would mean a lot to me. Obviously, you don't have to play it, but your feedback and criticism would help me make notes for future projects. Good luck with your future games. I will definitely check out any other games you release here.