Crashes or other problems with certain multimedia content in Firefox (such as Youtube videos and Flash animations or games) can often be resolved by performing the steps in these Knowledge Base articles:

• Flash Plugin - Keep it up to date and troubleshoot problems

• Adobe Flash plugin has crashed - Prevent it from happening again

• Flash 11.3 doesn't load video in Firefox

On Windows Vista and above, you can disable Flash protected mode by following the instructions on these pages:

• http://forums.adobe.com/thread/1018071#TemporaryWorkaround
• http://kb.mozillazine.org/Flash#Disabling_Protected_Mode_in_Flash_11.3

(See this Adobe blog post for technical details about Flash protected mode.)

For recent updates for Adobe Shockwave Flash, please update your version to 14. Please refer to the security updates and Adobe Security Bulletin for more information.

Please tell us if this helped!

Flash videos never play

If Flash videos may appear black, white or grey and never play, see Flash 11.3 doesn't load video in Firefox. Install missing plugins

Although Firefox can display some media on web pages such as images and open media like Ogg and WebM videos, it may need the help of media players and browser plugins for video, audio, and other content. Although you may have the correct media players installed to play video and audio files, you may be missing the necessary plugins when the media is embedded within the web page itself.

When a plugin is missing, a message will appear in place of the content:

   "A plugin is required to display this content" indicates that the plugin is not installed on your machine.

   flash required fx35

   "Activate (name of plugin)' indicates that the plugin might be installed, but isn't automatically activated.

   activate flash

If a link to download or activate the plugin does not appear, install the plugin manually by visiting the instructions for the plugin that you want:

   Flash plugin: See Install the Flash plugin to view videos, animations and games and Flash Plugin - Keep it up to date and troubleshoot problems
       The Flash plugin is used for many types of embedded audio and video, including YouTube.com videos. 
   Java plugin: Use the Java plugin to view interactive content on websites
   Silverlight plugin: See Use the Silverlight plugin to play audio and video
   Windows Media Player plugin: See Play Windows Media files in Firefox with the Windows Media plugin
       The Windows Media Player plugin will only play a specific few Windows media formats (.asf, .asx, .wm, .wma, .wax, .wmp, .wmv, and .wvx) unless the web page is specifically designed for Firefox and other Mozilla browsers. Internet Explorer will use Windows Media Player for many other formats like mp3 and midi, but Firefox will require another plugin, such as QuickTime. 
   QuickTime plugin: See Use the QuickTime plugin to play audio and video
       The QuickTime plugin can handle many different types of embedded media. On older operating systems, the QuickTime plugin may not be configured to handle some common file formats found online, such as embedded .mp3 audio on Windows XP. In such cases, you need to select the media formats you want QuickTime to play in Firefox in your QuickTime Preferences. 

For other, less common, media players and their plugins, see these websites:

   Shockwave
   RealPlayer
   VLC 

Update your plugins

Check that you have the latest versions of all your plugins.

   Go to our Plugin Check page and follow the links to update any plugins that are out of date. 

Allow Plugin Container in your Internet security program

Allow your Internet security software (including firewalls, antivirus programs, anti-spyware programs, and more) to trust plugin-container.exe also known as Plugin Container for Firefox. For detailed instructions, see Configure firewalls so that Firefox can access the Internet where in that case Firefox means Plugin Container for Firefox. Disable a conflicting plugin

If you have more than one plugin installed that can handle the same media type, this can cause a conflict that prevents some embedded media from playing. You may be able to fix the issue by disabling one of the plugins.

   Click the menu button New Fx Menu and choose Add-ons. The Add-ons Manager tab will open.
   In the Add-ons Manager tab, select the Plugins panel.
   In the list of plugins, select the plugin you wish to troubleshoot.
       If you want to disable the plugin, select Never Activate in its drop-down menu.
       If you want to re-enable the plugin, select Always Activate in its drop-down menu. 

For example, you may need to disable the VLC plugin to play embedded QuickTime or Windows Media content. For more information about troubleshooting problems caused by plugins, see the Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems article. Other solutions Clear the cache

See How to clear the Firefox cache. Disable interfering extensions or ad-blocking software

   Ad-blocking software, such as anti-banner filters of your Internet Security program, or extensions, such as Flashblock or Adblock Plus, can prevent audio or video content from playing. If the site works with ad-blocking disabled, you may want to add the site to your whitelist in your adblocker filter.
   Any Firefox extension can also block plugins. If the video or audio plays when you disable all extensions, then one of your extensions was causing the problem. For more information, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems. 

Check some Firefox settings

   Verify that cookies are enabled in the Privacy panel in the Options window. Verify that the site is not blocked in the Cookie Exceptions list.
   Allow the website as an exception in the Firefox pop-up blocker. The "Block pop-up windows" option is found in the Content panel of the Options window. 

Remove specific entries in the hosts file (advanced users)

If you use a hosts file, you can temporarily disable it by renaming it Xhosts. Or, you can edit the hosts file to remove specific entries such as ad.doubleclick.net that can cause videos on certain sites to fail (for more information, see this MozillaZine forum thread). To apply changes to your hosts file, you may need to flush the DNS cache by entering the command: ipconfig /flushdns in the Run dialog box on Windows.

If you have problems with current Shockwave Flash plugin versions then check this:

• see if there are updates for your graphics drive drivers

https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

• disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later)

https://forums.adobe.com/message/4468493#TemporaryWorkaround

• disable hardware acceleration in the Flash plugin

https://forums.adobe.com/thread/891337 See also:

• http://kb.mozillazine.org/Flash#Troubleshooting

Thanks for the help but nothing worked. We have the newest version of shockwave flashe, 16.0.0.235. Also noticed that all videos won't play.

Check these links and post there replies;

https://www.youtube.com/html5 Flash Player Test Page Shockwave Test Page

Adobe Support https://forums.adobe.com/community/flashplayer

Thanks for all the help.

some more info Videos work fine in Internet Explorer. It's just not youtube, i can't get any embedded videos to play.

I tried uninstalling firefox, restarting the machine, then reinstalling firefox. Same problem, videos won't play.

I think for some reason firefox doesn't "see" flash even though it will list in under plugins. I have no idea how to fix this.

I also went to the Flash Play test page (http://www.adobe.com/software/flash/about/) and that wouldn't work. Java is a fresh install and is working fine. Was able to play Minecraft.

Minecraft would be Java.

YouTube HTML5 Test

At this point, I would suggest you contact Adobe Support https://forums.adobe.com/community/flashplayer

Let us know what happens.

Good luck.