https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save '''Note:''' Some software, '''like''' Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

This can possibly be caused by a problem with the profiles.ini file or with the permissions of this file and other files in the profile folder. *Mac: ~/Library/Application Support/Firefox/ The ~/Library folder in the Home directory is a hidden folder. *http://kb.mozillazine.org/Show_hidden_files_and_folders#Mac_OS_X ---- It is possible that a new default-release profile folder has been created. See "Determine if Firefox has created a new profile": *https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks You can open the <b>about:profiles</b> page via the location bar to check whether multiple profiles are present and what profile Firefox currently is using. *Do NOT click any Remove button on this page. *https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles Firefox 67 and later can use a dedicated profile for each of the Firefox update channels and will lock the profile, so it can only be used by Firefox in a specific installation folder. For Release versions this profile would be a xxxxxxxx.default-release profile, profiles used in older Firefox versions usually used a xxxxxxxx.default profile (a refresh adds a time stamp). *https://support.mozilla.org/en-US/kb/dedicated-profiles-firefox-installation