Please try near page bottom Deleting : https://support.mozilla.org/en-US/kb/password-manager-remember-delete-change-and-import

If that does not work : https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save

Please let us know if this solved your issue or if need further assistance.

Make sure to keep the Site Preferences.

Note that clearing "Site Preferences" clears exceptions for cookies, images, pop-up windows, and software installation and exception for password and other website specific data

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