So I'm doing a project for school and had to edit this video I made that had an mp3 for some background music. I open iMovie up and try to play the video, but the audio has a "caution" looking sign in the top left corner and I can't hear anything. So I delete the audio and try to add it again, and it does not work. I drag and drop or copy and paste and nothing happens. Anyone know what to do? I need to have this done for Wednesday and this is the only thing holding me up.