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Unable to install add-ons

  • 5 replies
  • 2 have this problem
  • 50 views
  • Last reply by mmcnally

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When I visit any Add-ons page, instead of the button to install the add-on, a button stating "Only with Firefox - Get Firefox now" appears. Clicking this button takes me to the Firefox download page.

This is happening in Firefox, which just updated to the latest version (67.0.1) this morning.

Chosen solution

Your System Details list shows that you have a user.js file in the profile folder to initialize prefs each time Firefox starts. The user.js file will only be present if you or other software has created this file and normally won't be present.

You can check its content with a text editor (right-click: "Open with"; do not double-click). The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.

You can delete the user.js file if you didn't create this file yourself.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

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All Replies (5)

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The System Details list shows that you have a broken user agent that identifies you as Firefox 50

  • Mozilla/5.0 (Windows NT 6.1; WOW64; rv:50.0) Gecko/20161123 Firefox/50.0; xs-yXXal3WnNSs;

See:

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Separate Security Issue: Update your Flash Player or remove it using these links; Uninstall Flash Player | Windows {web link} Uninstall Flash Player | Mac {web link}

Note: Windows users should download the ActiveX for Internet Explorer. and the plugin for Plugin-based browsers (like Firefox).

Note: Windows 8 and Windows 10 have built-in flash players and Adobe will cause a conflict. Install the plugin only. Not the ActiveX.

Flash Player Version 32.0.0171

https://get.adobe.com/flashplayer/ Direct link scans current system and browser Note: Other software is offered in the download. <Windows Only>

https://get.adobe.com/flashplayer/otherversions/ Step 1: Select Operating System Step 2: Select A Version (Firefox, Win IE . . . .) Note: Other software is offered in the download. <Windows Only> +++++++++++++++++++ See if there are updates for your graphics drivers https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration

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I uninstalled Flash. I also followed the instructions for resetting the user agent and restarted Firefox. Firefox is still showing the wrong user agent in about:config.

What's my next option for correcting the user agent?

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Chosen Solution

Your System Details list shows that you have a user.js file in the profile folder to initialize prefs each time Firefox starts. The user.js file will only be present if you or other software has created this file and normally won't be present.

You can check its content with a text editor (right-click: "Open with"; do not double-click). The user.js file is read each time Firefox is started and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.

You can delete the user.js file if you didn't create this file yourself.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

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The user.js had a single line in it: user_pref("general.useragent.override", "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:50.0) Gecko/20161123 Firefox/50.0; xs-yXXal3WnNSs;"); I have no idea where that came from or why it was there.

I was able to delete the user.js and reset the general.useragent.override setting. After restarting Firefox all is working correctly again.

Thanks for your help!