Make sure that toolbars like the "Navigation Toolbar" and the "Bookmarks Toolbar" are visible: "View > Toolbars"

• If items are missing then open the Customize window via "View > Toolbars > Customize" or via "Firefox > Options > Toolbar Layout"
• If a missing item is in the toolbar palette then drag it back from the Customize window on the toolbar
• If you do not see an item on a toolbar and in the toolbar palette then click the "Restore Default Set" button to restore the default toolbar set up.

done all this but still cannot see a url in navigation box. Was OK in previous versions of firefox. Is there a way of fixing this?

Do you have the location bar visible on the Navigation Toolbar ?

If that bar is there and not working (grayed or read-only) then try to open a new window to see if that gives you a working location bar.

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.com/kb/Safe+Mode

• https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes

• http://kb.mozillazine.org/Menu_differences
• Windows: Firefox (Tools) > Options
• Mac: Firefox > Preferences
• Linux: Edit > Preferences