While removing your firefox, won't delete your profile. try with new profile.

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

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 the problem

Profile Backup and Restore

• http://kb.mozillazine.org/Profile_backup
• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

thanks for your replay i deleted the profile and created new one but same issue

thanks for your replay i deleted the profile and created new one but same issue

In case you have Adobe Flash installed on your system, would you please go to Options => Add-ons => Plugins and make sure that Shockwave Flash is set to 'Ask to Activate'  ?

Happy112 said

In case you have Adobe Flash installed on your system, would you please go to Options => Add-ons => Plugins and make sure that Shockwave Flash is set to 'Ask to Activate'  ?

it is already Ask to Activate and still not fixed but i found that if i installed extension like :((HTML5 Video Everywhere!)) it replaced youyube player to another player it is working but not perfect like old player is there any solution ??

lemo147 said

it is already Ask to Activate and still not fixed but i found that if i installed extension like :((HTML5 Video Everywhere!)) it replaced youyube player to another player it is working but not perfect like old player is there any solution ??

I was under the impression that you couldn't play videos on other sites
either (?) You shouldn't have to install 'HTML5 Video Everywhere' for YouTube, as YouTube uses HTML5 by default these days.

You could check this : https://www.youtube.com/html5?gl=NL

Another thing to try : Try disabling graphics hardware acceleration in Firefox. Since this feature was added to Firefox it has gradually improved but there are still a few glitches.

You will need to restart Firefox for this to take effect so save all work first (e.g., mail you are composing, online documents you're editing, etc.,) and then perform these steps:

In Firefox 54 and below:

1. Click the menu button and select Options (Windows) or Preferences (Mac, Linux).
2. Select the Advanced panel and the General tab.
3. Uncheck Use hardware acceleration when available.
4. Close Firefox completely and then restart Firefox to see if the problem persists.

In Firefox 55 and above:

1. Click the menu button and select Options (Windows) or Preferences (Mac, Linux).
2. Select the General panel.
3. Under Performance, uncheck Use recommended performance settings. Additional settings will be displayed.

   

4. Uncheck Use hardware acceleration when available.
5. Close Firefox completely and then restart Firefox to see if the problem persists.

Did this fix your problems? Please report back to us!

If the problem is resolved, you should check for updates for your graphics driver by following the steps mentioned in these Knowledge base articles:

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

• Upgrade your graphics drivers to use hardware acceleration and WebGL

Yes you are right graphics hardware acceleration is the reason when i disabled it videos working normally again

i will try to update now the graphic card driver 

thank you

My pleasure - I'm really glad you got things working again  !