This can happen if you run Firefox as Administrator as that allows you to make changes that you can't do as a normal user. You can open the Properties of the Firefox desktop shortcut via the right-click context menu and check the "Compatibility" tab. Make sure all items are deselected in the "Compatibility" tab of the Properties window. *Privilege Level: "Run this program as Administrator" should not be selected *"Run this program in compatibility mode for:" should not be selected Also check the Properties of the firefox.exe program in the Firefox program folder. See also: *https://support.mozilla.org/en-US/kb/enable-background-updates-firefox-windows