If you are using an external camera connected to your device you must make sure that it is selected in the system. You may need to allow access to your camera in permissions. Click the small lock icon to the right of the URL in your status bar. If you do not see the settings for camera immediately then click on the Site Settings selection and allow your camera access in the site settings page. After closing Site Settings you will need to reload the interview page for the camera access to take effect.