Try Firefox Safe Mode to see if the problem goes away. Firefox Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes).

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu:

• Click the menu button , click Help and select Restart with Add-ons Disabled.

If Firefox is not running, you can start Firefox in Safe Mode as follows:

• On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac: Hold the option key while starting Firefox.
• On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
  (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

When the Firefox Safe Mode window appears, select "Start in Safe Mode".

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, theme, or hardware acceleration. Please follow the steps in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help others with the same problem.

Hi Wesley,

The issue still occurs in Safe Mode.

Make sure you run Firefox in desktop mode and not in tablet mode.

• https://www.top-password.com/blog/windows-10-switch-between-tablet-mode-and-desktop-mode/

Hi Cor-el,

That toggle is greyed out for me, as I am on a desktop already, without a touchscreen.

Thanks

Go to your Firefox profile folder. If you see a chrome folder, check to see if there is a userChrome.css file in that folder.

Check for the same thing in your Firefox installation folder.

Try a different Windows theme or experiment with its settings to see if can find one that works.

Wesley, I did not see a userChrome.css file, or chrome folder, in the profile folder nor in the installation folder.

Cor-el, I tried both the "Window" and "Windows 10" themes that come pre-packaged with Windows 10, the icon is still missing.

Thanks.

Certain Firefox problems can be solved by performing a Clean reinstall. This means you remove your Firefox program files and then reinstall Firefox. This process does not remove your Firefox profile data (such as bookmarks and passwords), since that information is stored in a different location.

To do a clean reinstall of Firefox, please follow these steps: Note: You might want to print these steps or view them in another browser.

1. Download the latest Desktop version of Firefox from mozilla.org (or choose the download for your operating system and language from this page) and save the setup file to your computer.
2. After the download finishes, close all Firefox windows (or open the Firefox menu and click the close button ).
3. Delete the Firefox installation folder, which is located in one of these locations, by default:
   • Windows: (Note: Check both folders.)
     • C:\Program Files\Mozilla Firefox
     • C:\Program Files (x86)\Mozilla Firefox
   • Mac: Delete Firefox from the Applications folder.
   • Linux: If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see Install Firefox on Linux. If you downloaded and installed the binary package from the Firefox download page, simply remove the folder firefox in your home directory.
4. Now, go ahead and reinstall Firefox:
   1. Double-click the downloaded installation file and go through the steps of the installation wizard.
   2. Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.

More information about reinstalling Firefox can be found here.

WARNING: Do not use a third party uninstaller as part of this process. Doing so could permanently delete your Firefox profile data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. These cannot be easily recovered unless they have been backed up to an external device! See Back up and restore information in Firefox profiles.

Please report back to say if this helped you!

Hi Wesley,

I just tried the reinstall, deleted from both Program Files and Program Files (x86). Reinstalled using the installer that I just downloaded. The icon is still missing.

Thanks.

Try a different builtin Firefox theme or lightweight theme from the customize page.

cor-el said

Try a different builtin Firefox theme or lightweight theme from the customize page.

Interesting, this seems to work for some themes, but the 3 themes that come with Firefox: Default, Dark, and Light, don't work. There are also others on the add-ons page that do and don't work. For example: https://addons.mozilla.org/en-US/firefox/addon/pastel-gradient/ does work, however, https://addons.mozilla.org/en-US/firefox/addon/arc-dark-theme-we/?src=search does not.

Again, the default themes also do not work.

Thanks