I have just installed the Window Titler add-on for labelling Firefox windows. As soon as I did and as soon as I completed the step in the customise page to add Titles to windows (tick bottom left box), I have lost the functionality to select any of the overall standard Firefox Menu options across the top: everything from Firefox to Help are visible as per normal, but I can only actually click on 'Firefox' to make it do anything. File, Edit, View, History, Bookmarks, Tools, Window and Help are all there still but are unclickable - nothing happens on any of them. I can click the hamburger menu on a window toolbar and select menu options there. But the overall one is as above. How can I get it working?