I use OBS to livestream a church service every week. Two of the last three weeks have had no audio in the Youtube stream. Prior to that it has worked fine for several months. Sound source is a mixing board to camcorder, then HDMI from the camera to a HDMI to USB3 adapter to the laptop that feeds to Youtube. I also record to a SD card on the camcorder and audio is fine there, so problem is somewhere after the camera. When I look at OBS during the event, I see audio levels in the video capture device, so I assume I have good audio coming into OBS. Not sure what to check next.