Its quite a common situation that your browser won't let you click the various controls on the Flash permissions dialog.Sometimes you can use the keyboard to navigate to it, but the best way is probably to visit the Adobe/Macromedia settings pages. The local storage settings page is here. 

Grant permission to your webcam and mike to your Moodle site.

The global settings page, allows you to set default settings for any Flash enabled site that you visit (that you have not set individual settings for).