Do you have access to older key4.db copies that have a known or no Primary Password that you could possibly use ? You can look a utility to browse System Restore points. *https://www.shadowexplorer.com/ *https://www.nirsoft.net/utils/shadow_copy_view.html I think that safest might be to to create a new profile and connect that profile to the Sync account assuming you know the password of the Sync remember as resetting this account as well will complicate things futher. *https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles You can install the About Sync extension in Firefox 72 and newer on desktop to check what data is stored on the Sync server via the <b>about:sync</b> page provided by this extension. *About Sync https://addons.mozilla.org/firefox/addon/about-sync/ Close and restart Firefox to access the <b>about:sync</b> page added by this extension (see the about:about page for possible about pages).