Security Issue: Update your Flash Player '''Version 19.0.0.226<br>https://www.adobe.com/products/flashplayer/distribution3.html''' '''Note: Windows users''' should download the ‘’’active_x’’’ for “Internet Explorer,” '''and''' the ‘’’plugin’’’ for “Plugin-based browsers” (like Firefox). Note: Edge on Win10 does not use ActiveX version but its own Flash. See if there are updates for your graphics drivers https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration ------------ Note: Avast has been known to cause issues in Firefox. Disable it as a test. ----------- It is possible that there is a problem with the file(s) that store the extensions registry. Delete the extensions.* files (e.g. extensions.json, extensions.sqlite, extensions.ini) and compatibility.ini in the Firefox profile folder to reset the extensions registry. *https://support.mozilla.org/kb/Profiles New files will be created when required. See "Corrupt extension files": *http://kb.mozillazine.org/Unable_to_install_themes_or_extensions *https://support.mozilla.org/kb/Unable+to+install+add-ons