Nov 02, 2011 · Restart/ReBoot does not help. Firefox is in my start-up list and always says: "Close Firefox A copy of Firefox is already open Only one copy of Firefox can be open at a time". I click OK to flush the dialog box, then click Firefox to start it from the dock or Apps folder - same thing.
Firefox 23.0 canonical 1.0 already running not shutting down or starting up error. States its already running need to shut-down do system restart and close browser. Firefox 78.0.2, See All New Features, Updates and Fixes Jul 09, 2020 How To Uninstall Mozilla Firefox Completely From Computer Apr 24, 2020
Firefox: Change pop-up blocker settings, Enable JavaScript, or Clear the cache. If a SWF file stops abruptly, see Flash video stops after a few seconds in Firefox. Chrome: Chrome has a built-in Flash Player. Check if the internal Flash Player is interfering with external Flash Player. Type about://plugins into address bar. On the Plug-ins page
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Fix: Firefox is not responding - Appuals.com
Firefox not running after latest update, error AppHangB1 Aug 29, 2012 firefox not running in debian - LinuxQuestions.org