If this issues pertains to an add-on being broken, please contact the developer of the add-on so they can release and update and keep up to date with new releases Firefox has every 6 weeks.

Thanks!

Try to delete the pluginreg.dat file in the Firefox Profile Folder and maybe addons.sqlite as well to reset the plugin registry databases.

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder

You can (re)install the new WMP plugin (np-mswmp.dll)

• https://support.mozilla.org/kb/Using+the+Windows+Media+Player+plugin+with+Firefox
• http://kb.mozillazine.org/Windows_Media_Player#Missing_plugin

To feer56: Thank u for the advice. The wmp plugin is dated from 2007. I don't think this add-on is broken or not suitable after the latest update, because many users would then post this issue.

To cor-el: Thanks for the answer, however it didn't help. And when I tried to add the plugin manually firefox freezes or says the exe file is corrupted. I am almost sure the file is ok. I downloaded it from multiple sources but firefox refuses them all. I am wondering what could cause this.

It is possible that anti-virus software is corrupting downloaded files or is otherwise interfering with downloading files.

Try to disable the real-time (live) scanning of files in your anti-virus software temporarily to see if that makes downloading work.

See:

• http://kb.mozillazine.org/Unable_to_save_or_download_files
• browser.download.manager.scanWhenDone

I may have to disagree, if it is dated back to 2007 then chances are that there may be many issues. We receive reports of addons breaking all the time and so we get reports all the time.

Please contact the developer for more assistance.

I Think I have solved the problem. I didn't pay much attention to the version number. I Found out that I had Firefox 21. however app.update.channel was set to release. I installed version 20 and wmp plugin is working. I hope it won't update to 21 until it becomes a release version.

feer56 and cor-el; thanks for your help.

After upgrading to FF21, the WMP plugin disappears from the addon list, not suitable. Ok until FF20. Please fix this behaviour, otherwise a lot of websites become unuseful. Thanks.

Try to delete the pluginreg.dat file in the Firefox Profile Folder and maybe addons.sqlite as well to reset the plugin registry databases.

See Re-initializing the plugins database:

• https://support.mozilla.org/kb/troubleshoot-issues-with-plugins-fix-problems

Same problem. After updating to FF21, the Microsoft® Windows Media Player Firefox Plugin 1.0.0.8 np-mswmp is no longer listed in plug-ins as either enable or disabled.

Reinstalling the plug-in and deleting the pluginreg.dat file had no effect. Windows 7 Pro/SP1 64bit.

This is a bug! a lot of people does experience this issue...

Found a solution:

Go into about:config and change plugins.load_appdir_plugins from false to true. Apparently FF21 sets this value to false by default causing it to not detect plug-ins installed in this manner.

You must contact developers to push an update for their plugins. We do NOT make updates nor do we push them. We only notify and inform them. The developers have more than enough time to make their plug-ins work. Please check if your plug-in is up to date as if it is out of date then obviously the plug-in will not work. I hope that you will understand this.

Thank you!

No, I dont agree with you! absolutely! this is NOT due to the plugin developer, but to Mozilla. Mozilla modified the behaviour. Mozilla should to repair the issue! the plugin is NOT blacklisted by mozilla!!! therefore.... I am worried about your reply.

Since 2007 it has been not updated ever, but it worked until FF20, therefore.... ;) I dont understand why the Firefox developers encourage the users to switch to other browsers with this kind of replies.

Mozilla did NOT make any major changes. Every updates, plugins break due to security updates and fixes and other nits and pieces. Mozilla does not have the power to create a new plugin version nor update it on behalf of the developers. It is up to the developers to put an update out to fix. We cannot fix it because it has nothing to do with us making it not work. You reported this a while back using version 21. If you were using version 21, wouldn't the plugin have worked since you were not using version 20? Plug-ins break eventually and it's not because Mozilla doesn't care about it but developers are given more than enough time to fix or release updates for their plug-ins. We cannot do anything about the behavior, version 21 is released with no major changes so it is only up to the developers to fix the issue.

oh mozilla did NOT make changes, except this: >>o into about:config and change plugins.load_appdir_plugins from false to true. Apparently FF21 sets this value to false by default causing it to not detect plug-ins installed in this manner.

wouldn't the plugin have worked since you were not using version 20?

oh my god.

>> Found a solution: Go into about:config and change plugins.load_appdir_plugins from false to true.

BINGO! Thank you. How ridiculous that I have spent hours of frustration all because Mozilla broke the plugin load config in their new version...

And NO, the "developer" in this case should not be required to provide an Update to Mozilla.... the DEVELOPER of Windows Media Player IS MICROSOFT. Is this behavior now expected from new FF versions ??

but the expert say that mozilla did not change nothing in FF21... (nothing.... except this key!)  ;)