Join the AMA (Ask Me Anything) with the Firefox leadership team to celebrate Firefox 20th anniversary and discuss Firefox’s future on Mozilla Connect. Mark your calendar on Thursday, November 14, 18:00 - 20:00 UTC!

This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Avatar for Username

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

This thread was archived. Please ask a new question if you need help.

"The addon could not be downloaded because of a connection failure"

  • 1 reply
  • 7 have this problem
  • 1 view
  • Last reply by cor-el

gordongeise
gordongeise
more options

New Dell Precision 3800 running Windows 7. Installed latest Firefox from the Mozilla site. For the first time ever in my experience, Firefox is refusing various sites from asking to install add-ons. I click "Allow" and another alert shows up with the subject advice.

I've been through the help. The closest article advised me to add the site(s) trying to install add-ons to my "Exceptions" list under Options > Security > Warn me when sites try to install add-ons. But I don't even have that box checked, so "Exceptions" is grayed out.

I've Googled. Somebody a couple years ago suggested (and several others said "yay that worked") adding a string in about:config called xpinstall.enabled and making it "True". String sounded wrong so I tried Boolean. Didn't work. I tried string anyway. Didn't work. Nothing works except downloading the add-on install files and opening them with Firefox. That sucks. Now it's not even showing me an "Allow" button to click. Very. Very. Very. Very. Very. Frustrating. Very. Did I mention Very?

New Dell Precision 3800 running Windows 7. Installed latest Firefox from the Mozilla site. For the first time ever in my experience, Firefox is refusing various sites from asking to install add-ons. I click "Allow" and another alert shows up with the subject advice. I've been through the help. The closest article advised me to add the site(s) trying to install add-ons to my "Exceptions" list under Options > Security > Warn me when sites try to install add-ons. But I don't even have that box checked, so "Exceptions" is grayed out. I've Googled. Somebody a couple years ago suggested (and several others said "yay that worked") adding a string in about:config called xpinstall.enabled and making it "True". String sounded wrong so I tried Boolean. Didn't work. I tried string anyway. Didn't work. Nothing works except downloading the add-on install files and opening them with Firefox. That sucks. Now it's not even showing me an "Allow" button to click. Very. Very. Very. Very. Very. Frustrating. Very. Did I mention Very?

All Replies (1)

cor-el
cor-el
  • Moderator
  • Top 10 Contributor
more options

It is more likely that either an extension or other (possibly security) software is blocking downloading extensions. There shouldn't be any problems with downloading and installing an extension if you click the allow button.

You can inspect and manage the permissions for the domain in the currently selected tab via these steps:

  • Click the "Site Identity Button" (globe/padlock) on the location/address bar
  • Click "More Information" to open "Tools > Page Info" with the Security tab selected
  • Go to the Permissions tab (Tools > Page Info > Permissions) to check the permissions for the domain in the currently selected tab

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test.