AE crashes when I import mp4 files

I'm feeling extremely anxious because I'm unable to import .mov extension videos into After Effects. I attempted to convert them to mp4 by simply renaming the files from .mov to .mp4, but now, when I import the mp4 videos into After Effects, they become distorted, and the software crashes. I'm at a loss for what to do or who to turn to for help. I'm using a Mac, and I desperately NEED HELPPP