SAFE MODE

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

In Firefox Safe mode these changes are effective:

• all extensions are disabled (about:addons)
• default theme is used (no persona)
• userChrome.css and userContent.css are ignored (chrome folder)
• default toolbar layout is used (file: localstore-safe.rdf)
• Javascript JIT compilers are disabled (prefs: javascript.options.*jit)
• hardware acceleration is disabled (Options > Advanced > General)
• plugins are not affected
• preferences are not affected

TEST Please let us know if this solved your issue or if need further assistance.

That is possibly a problem caused by a Windows 10 insider update that breaks playing sound in Firefox.

• https://www.onmsft.com/news/windows-10-insider-build-17063-breaks-audio-in-firefox
• http://forums.mozillazine.org/viewtopic.php?f=38&t=3036696

• https://www.reddit.com/r/firefox/comments/7kxcf5/latest_windows_insider_build_broke_audio_in
• https://www.reddit.com/r/Windows10/comments/7kzt7s/psa_if_you_use_firefox_dont_upgrade_to_17063_it/

from 1426719 comment #38

Heads-up, Windows fix has reached mainline as of build 17073

So no workaround patch will be needed in Firefox 52 ESR and 57.0