I'm watching a source clip that was recorded with 8 channels of audio, but the actual sound is only on channels 1 and 2. When I try to drag the clip into the timeline, only channels 5-8 are dragged onto the timeline, so there's no sound. I can't figure out how to drag channels 1-4 as well.
Right-click clip in your bin, select Modify Audio Channels. Select only the 2 channels that have audio - ditch the rest.
You can select multiple clips at once and do the same if it was all shot the same.