Garageband recording automatically muted on mac

One section of my garageband recording automatically muted on MacBook Pro. I must've pressed something (maybe the letter M or N.) and now I'm having trouble undoing it. The whole recording plays until I get to this section. Then, the timeline goes grey and the mute button is activated.

I'll press the mute button and it deactivates and the sound returns. However, when I export it, that section mutes again. PLEASE HELP!!