Enabling Sound when playing videos during a meeting... Problem!

When we share our screen to show a PowerPoint during a meeting, we checked the box enabling computer sound when playing a video within the PowerPoint. This works fine on my computer, but when we do this on my friend's computer, checking that box immediately mutes her as the host and she cannot unmute herself unless she stops the share. It must be a setting issue, but we can't figure it out! Help!