Multicam/sequence audio missing

I've created multiple multicam clips which I edit into sequences. On one multicam clip the audio has stopped working - the file is still there but it is muted. When I open the MC clip on the timeline, all tracks are there,  and it is not muted. When I go to the source clips, audio is fine. On all other sequences I've been working on within the same project, audio is fine. So it is just in relation to this one multicam clip (being used for multiple sequences). When I try to replace the clips on the timeline, it still has no audio. I duplicated the clip, it also has no audio. The audio field is there, but it is muted somehow. I then tried to rebuild a new multicam clip and replace, but of course it won't sync up because it's an edited multicam clip. Any ideas? I'd love finding out how to restore the audio or I'd take just how to replace the multicam with a new one in which the audio works without having to redo hours of editing within the sequences. Thanks for any direction you can provide.