I had a very similar / the same? issue. Please check Firefox's Bugzilla for more details / troubleshooting steps if your issue is different:
https://bugzilla.mozilla.org/show_bug.cgi?id=1887735 (my) resolution steps: about:config CORRECT SETTING: media.rdd-process.enabled = true // Default My final troubleshooting steps: * A broken profile * A newly created 'clean' test profile (which worked, pointing me to a profile specific issue) * MOZ_LOG="PlatformDecoderModule:5" firefox --profile 7lnvxapn.TestTemplate Console output log * about:support Detailed summary including the missing RDD process breadcrumb.
