Keep going! Please do not stop because a viewer is reporting technical issues. The technical problem could be caused by their internet connection, local browser issues, or simply that their computer volume is turned down/off. Although it is tempting to stop the webinar, it is best to continue with your presentation so not to inconvenience your live audience, and impact the on-demand recording.
You can advise any viewers experiencing technical issues to email email@example.com - this is best achieved via the presenter-to-audience messaging panel with this icon: