Firefox users are reporting that their extensions and themes are not working after they have installed them. This problem seems to be affecting a lot of people, and there is no clear solution yet. So far, the most popular workaround is to uninstall Firefox, reinstall it, and then try the extensions and themes again. However, this process can be time-consuming and frustrating, especially if you have a lot of extensions and themes installed. Another workaround is to disable automatic updates for Firefox. This will prevent new updates from being installed, which may fix the problem with extensions and themes not working. However, this option may be difficult to use for some people because it requires a lot of control over their computer. ..
The Infamous Message Window
This is probably the most irritating message window that is associated with installing extensions or themes in Firefox. For whatever reason, you start the installation and get this. Not good at all! So what do you do about it?
Possible Work-Arounds
Try the following methods to see if one will help get those problem extensions or themes installed.
Method 1 – Enable Third Party Cookies
Go to the Tools Menu and select Options. Once the Options Window is open, choose the Privacy Tab Select “Use custom settings for history” to in order to access the additional options Make certain that “Accept third-party cookies” is selected Click “OK”. (Restarting Firefox is recommended)
Method 2 – Manually Install The Extension
Right click on the extension or theme install link and select “Save Link As” Once you have saved the extension or theme, drag the file into the Add-ons Manager Window with your mouse
Note: If for some reason manually installing the extension or theme still fails, there is a possibility that your anti-virus or another download monitoring software may be corrupting the file. In this case you could download the extension or theme on another computer and transfer it using a flash drive.
Method 3 – Clear The Cache
Go to the Tools Menu and select Options. Once the Options Window is open, choose the Privacy Tab Select “Use custom settings for history” to in order to access the additional options Select “Clear history when Firefox closes” and then click on the “Settings Button” Make certain that “Cache” is selected in the Settings Window (other options can all be deselected based on your needs) Restart Firefox
Method 4 – Restart Firefox After “Failed Add-on Installation”
If you are installing directly from the Mozilla Add-ons website, there could be a problem with the Mozilla Add-ons website database or with a broken mirror website. Restart Firefox to see if the extension or theme did install regardless of the“Invalid file hash (possible download corruption)” error message.
Method 5 – Other Alternatives
Try installing the extension or theme again at a later time Try installing the extension or theme from the add-on creator’s personal website
Hopefully with these tips you can bypass the error and enjoy more Firefox Add-on goodness.
