Firefox Bug fix: The add-on could not be downloaded due to a connection failure

If you cannot download and install an add-on and you see the error message “Add-on could not be downloaded due to connection error” in your Firefox browser, you can still download and install it. The error occurs because the server does not respond to the user’s request.

In addition, if you try to install a new extension from the official Firefox Addons website (, you will get the following error messages:

  • Download failed. Please check your connection.
  • The addon could not be downloaded due to a connection error.
  • The add-on downloaded from this site cannot be installed because it seems to be corrupted.

This article will help you solve the problem and install the add-on in Firefox.


What is the cause of the “Add-on cannot be downloaded due to connection error” error in Firefox?

What is the cause of the "Add-on cannot be downloaded due to connection error" error in Firefox?

Antivirus and other security programs can sometimes prevent Library Access extension in Firefox from automatically installing or updating. If this happens, please follow the steps below to successfully install our extension. This may be a temporary problem that will fix itself.


How to fix the “The extension cannot be loaded due to a connection error” error in Firefox

How to fix the "The extension cannot be loaded due to a connection error" error in Firefox

Download the extension manually

Before we get started, as we are downloading the file, I suggest using a third-party download manager. In case there are problems, you can continue with the download.

  1. Open the extension page and find the “Add to Firefox” button.
  2. If you are using a third-party website, look for the download link.
  3. Right-click the download link or the “Add to Firefox” button. Select “Save As.”
  4. It will be saved as a .xpi file. You can choose the default name or add your own.
  5. Press the Enter key to start the download.
  6. When the download is complete, when prompted, choose whether you want to open it in Firefox. The donation will be set.
  7. If not, you can choose to open it with Firefox.
Activate the XP install flag
  1. Go to the window: config and click on
  2. Type XP install. enabled to search for settings.
  3. Double-click to set it to true
Solution 3

By default, Mozilla Firefox checks the signature of installed add-ons and every time you want to install a new add-on or extension. You can disable this feature and forcibly install the required extension/extension without any problem. It will also restore existing add-ons that were automatically deactivated.

To disable this feature, you must set XP to install signatures required to false in the about config page. After disabling this feature, try to install the add-on and it will install without any problems. In addition, all previously installed add ons/extensions will be successfully enabled.

Solution 4
  1. Open the official Firefox extensions website ( and go to the extension/extension module you want to install.
  2. Right-click on the “+ Add to Firefox” button and select the “Save link as” option. The file with the XPI extension will be uploaded to your download folder.
  3. Now type about: debugging in the Firefox address bar and press Enter. The debugging page of the add-ons will open.
  4. Now click the “Download Temporary Add-on” button, go to the download folder and select .XPI file of the desired extension that you saved in step 2.

That is all there is to it. The extension/extension will install immediately without any error messages.

Note: The XPI file of existing add-ons/extensions will be saved in the Extensions folder of your Firefox profile. You can select the XPI file of all installed extensions one at a time in step 4 to reactivate disabled extensions in Firefox.

These solutions should be enough to load the extension in case of a connection failure, but sometimes you will have to wait. This can be a temporary problem that will fix itself. In the end, I recommend using VPN software. If your ISP is blocking something, a VPN connection should be able to fix it.


Frequently Asked Questions

The problem with add-ons may be caused by a temporary bug in Firefox. The problem can be solved by disabling and enabling Firefox add-ons, which solves the problem. This action will reset and restart all add-ons. If not, install another addon to see if Firefox works correctly again.

All old addons have been disabled at (AMO). Users will no longer be able to find old addons on AMO. If you choose to use unsupported versions of old add-ons, it will leave you vulnerable to security holes and we strongly recommend that you do not use them.

  1. Click on the menu button and select Options.
  2. In the General section, go to Proxy Network Settings.
  3. Click the Settings button. The Connection Settings dialog box will open.
  4. Change the proxy settings.
  5. Close the Connection Settings dialog box.
  6. Close the About: Preferences page.

Make sure your device is connected to the Internet. If the Internet is working fine, restart your device. This will update the operating system and application and may solve the problem. If you are only having problems with some addons, it may be a server issue.

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Mark Ginter is a tech blogger with a passion for all things gadgets and gizmos. A self-proclaimed "geek", Mark has been blogging about technology for over 15 years. His blog,, covers a wide range of topics including new product releases, industry news, and tips and tricks for getting the most out of your devices. If you're looking for someone who can keep you up-to-date with all the latest tech news and developments, then be sure to follow him over at Microsoft.