Fix: The add-on could not be downloaded because of a connection failure Firefox error

Updated May 2024: Stop getting error messages and slow down your system with our optimization tool. Get it now at this link
  1. Download and install the repair tool here.
  2. Let it scan your computer.
  3. The tool will then repair your computer.

Antivirus and other security software can sometimes prevent the Library Access extension from being automatically installed or updated in Firefox.

In this case, please follow the steps described below to successfully install the extension.

Failure to install an extension may be the result of problems with the extension, Firefox settings, or the version of Firefox you are using. This article describes several causes of installation problems and what you can do to solve them.

Download the extension manually

Just before we start, as we are downloading a file, I suggest using a download manager. If there is a problem, you can resume the download.

May 2024 Update:

You can now prevent PC problems by using this tool, such as protecting you against file loss and malware. Additionally it is a great way to optimize your computer for maximum performance. The program fixes common errors that might occur on Windows systems with ease - no need for hours of troubleshooting when you have the perfect solution at your fingertips:

  • Step 1 : Download PC Repair & Optimizer Tool (Windows 10, 8, 7, XP, Vista – Microsoft Gold Certified).
  • Step 2 : Click “Start Scan” to find Windows registry issues that could be causing PC problems.
  • Step 3 : Click “Repair All” to fix all issues.


  • Open the Add-on page and look for the Add to Firefox button. If you are using a third party website, look for the download link.
  • Right-click the download link or click the Add to Firefox button. Select Save As.
  • It is saved as an .xpi file. You can choose the default name or add your own name.
  • Press the Enter key to start the download.
  • Once the download is complete, choose to open the file in Firefox if necessary. The addon will then be installed. Alternatively, you can choose to open it in Firefox.

Enable the xpinstall flag

  • Go to about:config and click on the “I’ll be careful, I promise” button.
  • Type xpinstall.enabled to find the settings
  • Double-click on the value true

Delete the Recent Firefox History

  • Press the ALT key or press F10 to display the menu bar.
  • Go to the Tools menu -> Clear Last Used History -> Period to Clear: select “ALL” -> click the Details button (small arrow) -> check the Cookies, Cache, Website Settings boxes -> click Clear Now
  • Go to the menu Tools -> Options -> Security -> check the boxes :
    • 1) Warn me when sites try to install add-ons 2) Block reported attack sites 3) Block reported fake web sites
  • Go to Tools -> Options -> Advanced -> Network -> Offline Memory (Cache): Click the Delete Now button
  • Click OK in the Options window -> Restart Firefox

Expert Tip: This repair tool scans the repositories and replaces corrupt or missing files if none of these methods have worked. It works well in most cases where the problem is due to system corruption. This tool will also optimize your system to maximize performance. It can be downloaded by Clicking Here