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

RECOMMENDED: Click here to fix Windows errors and optimize system performance

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.

June 2020 Update:

We now recommend using this tool for your error. Additionally, this tool fixes common computer errors, protects you against file loss, malware, hardware failures and optimizes your PC for maximum performance. You can fix your PC problems quickly and prevent others from happening with this software:

  • 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

RECOMMENDED: Click here to troubleshoot Windows errors and optimize system performance