The request to allow access to your camera and microphone is usually generated in a pop-up window close to the top of the browser window. If you don't see the request window that may be due to a pop-up blocker you have set within your browser. Please disable it and then re-load the page to allow the permissions request to appear.  You can also go directly in by clicking on the little lock icon just to the left of the URL and allowing the camera in the application.