Still no answers :(

This sounds like a very broad issue, so until we can narrow it down, I would suggest going through the KB article for missing AV: https://support.mozilla.org/en-US/kb/fix-common-audio-and-video-issues.

To me it sounds like the content is simply being blocked (a black screen is very typical here) or the player components are missing; see the plugin container and HTML5 sections in the link above. Check if you can get extra info out of Youtube by right-clicking on the video and selecting Stats for nerds.

44.0 also has an issue where people have trouble connecting (stuck loading) and Firefox crashes on exit, but if browsing is otherwise unaffected, this may not be related to that.

At least i know its not just me :) black screen

Video ID: u9Dg-g7t2l4 Dimensions: 0 x 0 Resolution: 1280 x 720@24 Volume: 100% Stream Host: r7---sn-2a0noxu-ajts Stream Type: https CPN: ArXlw80ekfaWEE_s Mime Type: video/mp4; codecs="avc1.4d401f" DASH: yes (136/251) Connection Speed: 30449 Kbps Dropped Frames: 0/24

What worries me there is "Dimensions: 0 x 0".

It is definitely as you said, the video component is not expanding correctly. At least it seems to initiate (picks a codec, streams, draws frames).

I've gone through issues new and old but I can't find anything like this - typical solutions have been disabling an extension that was either conflicting with a player or blocking it completely. In your Extensions the following fit the profile:

Adblock Plus 2.7.1 Flash Control 2.1.3 YouTube High Definition 44.1.

If you disable ABP ("Disable on Youtube.com" from its own menu) and uninstall the other two from Firefox, is the problem still the same?

Yes i have tried restart without addons , and done a fresh install of FF 44 with no addons i am now using Beta 45-ob2 still same . yet all works correctly when i use palemoon x64 but not the 32 version ??

Create a new profile as a test to check if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) to see if that helps.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/
• http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10

OK i restart in safe mode / network , video not working . I Uninstalled all browsers with Revo uninstaller removed all folders . Clear cache/cookies with Ccleaner open regedit removed all mozilla references ran Malwarebytes nothing found restart , reinstall clean FF44 no sync , :( still no video,s except utbe runs with no sound unless sound is set to stereo no 5.1 BBC ,4OD etc no good

Firefox 44 x64 will play all videos if on stereo not 5.1 . but not on FF 44 x86

Thank you for being extremely diligent with the cleanup and retries!

This could be a manifestation of the 44.0 no-connection-crash-on-exit issue or a new 44.0 issue if a 64-bit build works but 32-bit doesn't. Some computers have this issue, and there is no word yet what exactly is the cause, so I can't offer a solution - the workaround is to go x64 as you have done, or to downgrade to 43.0.4 32-bit (no real loss there) until the problem is fixed.

I think I am out of options for now, so the workarounds would be what I would suggest. I put off updating to 44.0 myself due to similar concerns, but for me it runs fine for now (knock on wood).

Update , after several weeks now of trying different settings/drivers FF44.02 still incapable of playing video,s  :( have tried the flash player add on but it just crashes flashplayer Utube plays but without sound unless i set speakers to stereo not 5.1 which worked on previous FF , and still works on Chrome  !! I have used FF for last 10 or more years without any problems Please fix my Firefox i dont want too be using Chrome for too much longer

Ok just update to FF45 , still same problem Videos on BBC i player just gives a black screen same as other streaming sites , except utube where videoos play with no sound :(

Still no Fix :(

Still getting black screen on videos , :(