I have a php file with an html video tag which recently stopped working in Firefox Developer Edition (FDE). It still works in other browsers. In FDE, the volume is permanently muted. I can't find a way to turn mute off. In About:Config under Media: there are messages at media.decoder-doctor.new-issue-endpoint = https://webcompat.com/issues/new and media.decoder-doctor.notifications-allowed = MediaWMFNeeded,MediaWidevineNoWMF,MediaCannotInitializePulseAudio,MediaCannotPlayNoDecoders,MediaUnsupportedLibavcodec,MediaPlatformDecoderNotFound The partial source code is: <video onclick='playPause()' width='100%' controls muted> <source src='/videos/".$trimDir."/".basename($s)."' type='video/mp4'> </video>