See this thread as it may answer your question: https://support.mozilla.org/en-US/questions/1036385

Also see; Firefox 80+ has a logins-backup.json file in the profile folder that can be used in case of issues with logins.json or to undo an accidental delete of a login, so you can check if you can find this file in the profile folder or in a backup and replace the current logins.json. Make sure to keep a backup copy of all involved files (logins.json and key4.db and logins-backup.json) You can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page. Help -> More Troubleshooting Information -> Profile Folder/Directory: Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data If you use a Primary Password then you can prevent losing passwords by canceling the PP prompt. You need to logout beforehand by canceling a PP prompt, e.g. by clicking the eye icon in Lockwise (about:logins). Also see; https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update ------------- In the event that the passwords information is lost, you should record all information in a separate text file somewhere else on your hard drive, or written down. You can easily copy and paste if you need to do so. If you are concerned about someone else looking at that file, you can compress it using a password.