Hmm, not sure. You may have noticed the shield icon at the left end of the address bar is a bit purplish. That indicates the Tracking Protection feature is blocking something in the page. Could you click the shield and turn off protection on the page temporarily -- just click the slider switch at the top of the drop-down panel -- and see whether that makes any difference?

Also, thank you for sharing your Add-ons list. If you temporarily disable both of these two extensions, does that make any difference:

• Disable Autoplay
• Disable HTML5 Autoplay

You seem to have rather old display drivers, you can check if there is an update available.

Your troubleshooting information shows several extensions that can block autoplay, so it is quite possible that one of them is causing this problem

• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

1: {name: Autoplay No More, type: extension, version: 0.3.8, isActive: TRUE, id: jid1-XQEcUtyD5PwB8w@jetpack}
4: {name: Disable Autoplay, type: extension, version: 1.2, isActive: TRUE, id: {6674730a-e591-43c6-8680-d332ea121cc2}}
5: {name: Disable HTML5 Autoplay, type: extension, version: 2018.10.3, isActive: TRUE, id: disable-html5-autoplay@afnankhan}

Thanks for the prompt replies. The shield fence was for facebook container. I had 3 blockers and the html5 blocker was the problem. By disabling it OFF and leaving the others ON the problem seems to have gone. The other blockers don't cause a problem. I now have to see which videos or webpages will not block autoplay.

Happy New year!!

You can look at these prefs on the the about:config page to see what settings work for you to block autoplay.

• media.autoplay.default = 5 [0:allow;1:blockAudible;2:Prompt;5:blockAll]
• media.autoplay.blocking_policy = 2
• media.autoplay.allow-extension-background-pages = false
• media.autoplay.block-event.enabled = true

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

• https://support.mozilla.org/en-US/kb/block-autoplay