Have you checked in the Passwords menu to see if it's been stored or not? You can access it by clicking the orange Firefox button, go to Options | Options | Security.

Next, click the "Saved Passwords" button, then click "Show Passwords".

Passwords will not be saved if you browse in Private Browsing mode too.

See this article for more information: Security panel - Passwords

See also:

• http://kb.mozillazine.org/Preferences_not_saved
  
  
• http://kb.mozillazine.org/User_name_and_password_not_remembered
  
  

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Thanks.

Make sure that you do not run Firefox in permanent Private Browsing mode.

• https://support.mozilla.com/kb/Private+Browsing
• You enter Private Browsing mode if you select: Tools > Options > Privacy > History: Firefox will: "Never Remember History"
• To see all History and Cookie settings, choose: Tools > Options > Privacy, choose the setting Firefox will: Use custom settings for history
• Deselect: [ ] "Permanent Private Browsing mode"

• http://kb.mozillazine.org/Password_Manager