When i add a camrra layer my audio wont play

Impossible to know anything. You have not provided any info about the project such where and how the audio is used, what else is going on in the composition, your preview settings, system info and so on. You need to be much more specific. Simply adding a camera layer does not/ should not have any effect on previewing audio, so something specific is going on, but without at least soem useful info nobody can tell you what it might be.

Mylenium