Do you have it installed in your app folder or are you running it from the dmg file you downloaded?

Like posted above, make sure you install Firefox properly. Open the Firefox Disk Images file and drag the Firefox application to the Applications folder on your hard drive. You shouldn't double-click the Firefox application to run it from the Disk Images, but instead drag it out of the DMG folder. <hr> *https://support.mozilla.org/en-US/kb/install-firefox-mac You may want to cleanup unused profiles via about:profiles or via the Profile Manager. *https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles