I have had folks recently with audio issues go to the GoTo Control Panel and select No Audio, then reselect Computer Audio. That clears up a lot of audio connectivity problems. We should not have to do that.
@DL2 The GoToWebinar Um-mute All function is a soft-mute control that should allow participants to un-mute their own audio lines. If this should fail for whatever reason, then you may call into Customer Support from an affected machine in order to grant them access to the program log files for a full review.