Flash plugin not working

If Adobe's Test Page does not show that Flash is working even though you have installed the latest version, your Flash plugin may be disabled. To make sure that Flash is enabled,

   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.

If the Flash plugin is disabled, select Always Activate in its drop-down menu. The Adobe Flash plugin has crashed

If you see this message instead of Flash content, see Adobe Flash plugin has crashed - Prevent it from happening again. Unresponsive plugin warning

Firefox will show you a warning dialog if the Flash plugin is taking longer then expected:

   warning-unresponsive-plugin

See the article Warning Unresponsive plugin - What it means and how to fix it for solutions and workarounds. Playing Flash videos makes Firefox hang

If Firefox stops responding or if the Flash plugin hangs or stops working when playing Flash videos or games, try these solutions:

   Pause or stop Flash in other tabs. You may need to close those tabs.
   Update Flash. See the Updating Flash section above for instructions.
   Update your graphics drivers. See Upgrade your graphics drivers to use hardware acceleration and WebGL for details. 

   Disable hardware acceleration in Flash:
       Go to this Adobe Flash Player Help page.
       Right-click on the Flash Player logo on that page, then click on Settings in the context menu. The Adobe Flash Player Settings screen will open.
       Click on the icon at the bottom-left of the Adobe Flash Player Settings window to open the Display panel.
       Remove the check mark from Enable hardware acceleration.

       fpSettings1.PNG
       Click Close to close the Adobe Flash Player Settings Window.
       Restart Firefox. 

Cannot view full screen Flash videos

See Flash video won't play full screen on YouTube, Facebook and other websites. Flash does not work properly and/or will not update

If Flash content does not work, acts strangely, or causes errors, or if you see a notice that you need to update Flash (for instance, at Mozilla's Plugin Check) even after installing the latest Flash version, uninstall and reinstall Flash. Flash doesn't load video

If Flash videos or games may appear, black, white or grey and never play, see Flash 11.3 doesn't load video in Firefox. Flash works in Internet Explorer or Chrome but not in Firefox

There are three different types of Flash Players: an ActiveX version for Internet Explorer, a Chrome version built-in the browser and a plugin version for Firefox and some other browsers. If you want Flash to work in Firefox you must install the plugin version, as explained above.

Based on information from Flash (mozillaZine KB)

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