Sometimes, the video or audio content in a web page cannot be properly downloaded and displayed in Firefox. A required plugin may be missing, outdated, blocked, in conflict with another plugin or extension, or the content may be blocked for some reason. This article will help you solve these problems.
First off, make sure you're volume isn't on mute. You can test your speakers here: http://www.testmyspeakers.com/. When allowing permissions in your browser, make sure the right microphone is selected. Sometimes simply leaving the conference room, and re-entering can help. Also, try reloading your browser. If you continue to have issues, try switching to Chrome, then contacting firstname.lastname@example.org.