Voiceovers Have No Sound

iMovie 10.0.9

I recently went to record a voiceover in a movie I'm working on. I click the red "Start Recording" button, I get the 3-2-1- countdown, and I see the audio levels jump around as I'm recording. I stop the recording and the voiceover appears under the clip. However, the voiceover clip has no audio. There are no audio levels on the clip either (i.e. this isn't a speaker issue). This happens both when I'm recording through the mic built into my apple headphones, or through the built-in mic on my macbook pro. I have verified that both the headphones' mic and the macbook's mic are functioning (they work in all other applications, and are even transmitting sound in iMovie, as I can see the sound levels jumping around while recording the voiceover).

Any help would be much appreciated.