I'm having this issue as well. When I join everything is good. If I disable my webcam, audio is no longer transmitted to other conference participants. If I disable / enable my mic it usually comes back.
Further Notes:
Even when audio is not working, the level indicator next to my name continues to modulate showing that it is picking up audio from my mic.
This is for a web conference, which we have mostly been using. I don't know if this effects web meetings, but will verify.
After testing here is what I have found:
1. Seems to only effect web conferences, not having this issue in the ad-hoc webmeetings.
2. Only happens when my audio input device is a different device than my video input device.
3. When effected, toggling the mic mute will bring audio back.
For example, I'm using a Logi C920 webcam, but using my headset as the audio input device. And this is easy to reproduce, happens every time for me under these circumstances.
Thanks!