Did you check your Plugins list to see whether it is at the bottom in the disabled plugins section?

orange Firefox button (or Tools menu) > Add-ons > Plugins category

If it is disabled, can it be re-enabled or does it seem to be blocked?

If it's not there at all, it's possible that Firefox's plugin database file has become corrupted. You could try renaming that file and having Firefox regenerate it. The steps for that would be:

(1) Open your current Firefox settings (AKA Firefox profile) folder using

Help > Troubleshooting Information > "Show Folder" button

(2) Switch back to Firefox and Exit

(3) Pause while Firefox finishes its cleanup, then rename pluginreg.dat to something like pluginreg.old

(4) Restart Firefox. Assuming the DjVu plugin is listed in the registry or located in a Firefox-relevant folder, Firefox should find it.

Any luck?

If the result of the above operation is that Firefox cannot find most of your old plugins, you may have disabled plugin scanning. To check that:

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the filter box, type or paste scan and pause while the list is filtered

(3) If plugin.scan.plid.all is set to false, double-click it (or right-click > Reset) to switch it to its default value of true. I think you'll have to restart Firefox again to trigger the scan.

Hopefully, that covers all the possibilities...

Where was this plugin installed previously?

If this is in the plugins folder in the Firefox program folder then move this plugins folder to the browser folder.

• (32 bit Windows) "C:\Program Files\Mozilla Firefox\browser\plugins\"
• (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\browser\plugins\"

Alternatively you can set the plugins.load_appdir_plugins pref to true on the about:config page to see if this helps.

See also:

• https://developer.mozilla.org/en/Gecko_Plugin_API_Reference/Plug-in_Basics#How_Gecko_finds_plug-ins

Thanks for your reply, but no joy.

Yes, I had already checked to see if the DjVu plugin was at the bottom of the page/disabled. It was and is not.

I tried your steps for regenerating the file - no joy there either, and could not even get back to the support page to reply to you without reversing the process.

plugin.scan.plid.all is NOT set to false.

Any other suggestions?

Thanks.

Thank you for your reply cor-el.

Who knows where it was installed previously. Since the instructions from the site told me to uninstall the old version before attempting to install the new, it's gone, so I don't know where it was.

I do not find it listed in any of the locations you suggested (either the browser folder or the plugins folder).

Your suggestion to toggle the plugsin.load_appdir_plugins pref did bring it back from the dead.

Thank you.

Same problem. Updated Firefox 21 and Microsoft update between working yesterday and not working today. Using Windows XP. DjVu works in IE 8.

See this:
http://www.ghacks.net/2013/05/15/why-you-may-have-lost-access-to-plugins-or-extensions-in-firefox-21/

Maybe this is the plugin you are looking for: Caminova Djvu plugin.

For me, it's just doing what it's supposed to do : display djvu publications in both ie and firefox (24.0).

Hope this will help.

No offense intended, but do you really think I have been sitting here, doing nothing for 5 months?

It would be useful if people actually paid attention to the dates on posts.

Actually, I was trying to help here... and since you did not post the solution that you found, it is only fair (at least to other users) to point in the good direction.

And for your information, yes, I did check for the date of the post, but still, there was no good solution to your problem and yet other people had the same issue.

It would be helpful if people actually followed on their post to give back the solution that they found.

WOW don't you feel important! I should have told you - when I did not know you existed - that I was not waiting to hear from you.