I got a problem here, and that's not the first time.
When I had join a meeting via GoTomeetings software on laptop, I had tested and the video and audio working fine before the meeting. During meeting, my mic on webcam can recevied my voice at first. After around 2-3 hours, the webcam mic suddenly can't receive any voice, but the video is still working fine.
I check in setting windows, it doesn't show any signal on receiving voice, then I try to select the mic on laptop, and then switch to the mic on webcam, everything go fine again.
What you're describing sounds like the webcam microphone may have a safety feature engaging that assumes you won't need your microphone active for that long, or possibly the PC in use has an outdated audio driver that drops the connection at some point. I would suggest checking with both of these manufacturers for all available driver updates before testing the connection again.