Where are you trying to enter the master password?

• Options/Preferences -> Privacy & Security: Logins & Passwords: "Saved Logins" -> "Show Passwords"

The master password is stored in the key4.db file in the profile folder.

What security software do you have? There have been reports that AVG/Avast is causing issues with passwords disappearing. You can check the profile folder to see if there are logins.json.corrupt files present. If you find such a file then try to rename to logins.json.

• keep a backup copy of all logins.json files

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

I've attached a photo of what I see when click "use master password". It shows my current password as not set.

Our company uses Trend Micro Officescan.

There do not appear to be any corrupt logins.json files when I review the profiles folder.

My laptop at home has not had a new operating system upgrade, firefox was synced between the two, is it possible for me to copy something from the laptop to restore to the desktop with the new operating system? I know my password is correct, I used it just last week.

Try to rename/remove pkcs11.txt and secmode.db when present in the Firefox profile folder with Firefox closed.

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Moving or renaming the pkcs.txt while firefox is closed doesn't change anything. The secmode.db doesn't exist in my profile folder.

Any other suggestions?

If there is currently no master password set then it looks that the key4.db key file that stores the encryption key is corrupted or replaced.

Do you still see a logins.json file in the profile folder that contains login data if you open this file in a Firefox tab or plain text editor?

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

If you do not have the logins.json, but you do have a logins.json.corrupt file then rename this logins.json.corrupt file to logins.json. That way you have at least a possible password file. Next is to check if there is a possible key3.db file used previously as the key file.

Keep a backup of logins.json and key4.db and key3.db in a safe place before proceeding.

If you have key3.db then rename the current key4.db file (key4OLD.db), so you only have logins.json and key3.db left in the profile folder. Start Firefox and check if this restores passwords in the Password Manager. If that didn't work then you need to look for older copies of key4.db or key3.db that Windows might have saved as part of a System Restore point. You can check for older copies of logins.json as well because logins.json and the key file need to match.

You can look at this utility to browse System Restore points.

• System Restore Explorer
  https://www.nicbedford.co.uk/software/systemrestoreexplorer/

You need a matching pair of logins.json and key4.db or possibly key3.db. If you use a key3.db file then make sure to remove (rename) key4.db to hide it from Firefox.