Managed to upload the photos of my system info

Normally those media feature packs are for those who have say a N or KN version of Windows, 7,8,10 https://support.mozilla.org/en-US/kb/fix-video-audio-problems-firefox-windows

A couple of pages you can test to see what you support is https://www.youtube.com/html5 and the videos on https://www.quirksmode.org/html5/tests/video.html (ignore the ancient table on top).

Maybe you have one or more Extensions that can interfere like youtube flash or HTML5 related ones installed.

Thanks James I will check those out

If I were you stay away from Windows codec from Windows itself. I find that causes more problems then it helps.

Try this site I found these codec to be more useful but there are some ads on the page but just click on the codec. But when install use custom and go slowly cause there will be one last page where it ask to install some kinda software and I choose "Decline" and then finish the install. So do it Custom only.

http://www.codecguide.com/download_kl.htm

Otherwise you can always download VLC and that plays most videos without problems.

https://www.softexia.com/windows/multimedia/players/vlc-media-player

WestEnd said

If I were you stay away from Windows codec from Windows itself. I find that causes more problems then it helps.

You missed the point, the OP thought one needed to install the media feature pack when the poster does not appear to have say a K or KN edition of Windows. Windows installed in USA and Canada for example comes with the needed codecs.

I would say the Windows media feature packs from Microsoft are safe to install for those who needed it because of using a edition of Windows that does not come with it.

Had another Firefox update today and it seems to have fixed the problem. YouTube videos are now playing. Thank you both for trying to help, much appreciated.

Hmm there is a new a Firefox 58.0.1 update today but not for this issue.

https://www.mozilla.org/firefox/58.0.1/releasenotes/

And the Firefox update from today has stopped videos from playing again.

They are obivously not being completely truthful about what the updates are...

The minor Firefox updates are for security and allowed stability fixes. Unlike with some other companies that make web browsers, Mozilla is rather honest

For example https://www.mozilla.org/en-US/security/known-vulnerabilities/firefox/ Due to this openness some people mistakenly thought Firefox was more vulnerable as other browsers may companies barely reveal vulnerabilities over the years.

Well there is definitely something in the previous and current update that has to do with video playback but they have not disclosed. Absolutely nothing has changed on my laptop since the problem started except those two Firefox updates...but it no longer matters because I am switching to a different browser now.

disabling recommended performance settings and hardware acceleration in options>general>performance fixed it