Yesterday I did also a test for the first time with multicam. Also no audio in the multicam timeline.
Then I found out that only soundtrack 1 is used in the multicam timeline.
In the original timeline, soundtrack 1 was switched off, because I will use only the sound of track 3 and 4.
Now I will try to copy/past track 3 and 4 to the multicam timeline.
Maybe something like that is your problem too.
Good luck
Phocas Kroon