Hi coaboy, Thank you for your question. I understand that Flash player is not playing on a Windows 10 computer with Firefox. I am happy to help.

• Does this happen on various sites? If not, check to make sure that the plugin is not blocked for that site in the permission settings. (Right click on the page and select "Page Info" -> Permissions tab)

• Have you tried to disable hardware acceleration: Flash Plugin - Keep it up to date and troubleshoot problems

NO, every sites with flash banner, animation or video player based on flash not working. Also I try to disable hardware acceleration but same thing happening.

Hi there.

Since you already checked the plugin permissions and hardware acceleration, this smacks of either interference or straight-up blocking. It could still be a playback issue, of course.

Interference could be coming from Quicktime. Does the issue remain if you disable/uninstall the Quicktime plugin?

I can't see AdBlock Plus or any other blocking add-ons in your UI. Are you using any content blockers or filters?

Lastly, do your other browsers work with the latest Flash plugin (when you install all their separate packages)?

Start Firefox in Safe Mode to check if one of the extensions (3-bar Menu button/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: 3-bar Menu button/Tools > Add-ons > Appearance
• Do NOT click the Reset button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

You can check for problems with current Shockwave Flash plugin versions and hardware acceleration in Firefox and try this:

• make sure you have the latest Flash version:
  http://www.adobe.com/special/products/flashplayer/fp_distribution3.html
• check for updates for your graphics drive drivers
  https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration
• disable protected mode in the Flash plugin (Windows Vista and later)
  https://support.mozilla.org/kb/adobe-flash-protected-mode-firefox
• disable hardware acceleration in the Flash plugin
  https://helpx.adobe.com/flash-player/kb/video-playback-issues.html
• disable hardware acceleration in Firefox
  https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

See also:

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

@cor-el thanks a lot. Problem solved when I disable protected mode in the Flash.

You're welcome.

This is a problem here in the new 14257 build as well. There are numerous posts in the Windows Feedback tool about it, though they all still mention 14251 at this point.

Oddly, Protected Mode isn't a problem in some other Mozilla-based browsers that use the same plugin, such as Cyberfox, or non-Mozilla browsers that also use it, like Opera 12.

Just as an update, neither 44.0.1 nor today's Flash 20.0.0.306 updates remedied this. Will report back with the next Windows build.

No-go on 14271 (x64) and 44.0.2 (x86).

No-go on 14279 (x64) and 45.0 (x86) RC2.

I'm beginning to wonder in which of the three (Flash included) the bug lies.

No with 14316 (x64), Flash 21.0.0.197, and FF 45.0.1 (x86).

How long will this go on?

Not working in FF 45.0.1 on Ubuntu 14.04 LTS either

When this was fixed exactly I don't know, since I stopped checking, but Insider build 14385, plus Flash 22.0.0.209, plus Firefox 47.0.1 now work when Protected Mode is enabled.