If you or someone else had turned off automatic updates on Firefox, it is recommended that you turn it on. The procedure is similar to disabling the updater and here it goes:
1. On the Firefox menu bar, select ‘Tools‘–> ‘Options‘.
2. Click the ‘Advanced‘icon in the window.
3. Click on ‘Update‘tab. The auto-update options are displayed.
To turn on all automatic updates, check all the 3 options that are visible, i.e, check – Firefox, Add-ons and Search Engines.