App (pinned) tabs and Tab Groups (Panorama) are stored as part of the session data in the file sessionstore.js in the Firefox profile folder.

• http://kb.mozillazine.org/Profile_folder_-_Firefox Firefox
• http://kb.mozillazine.org/sessionstore.js
• http://kb.mozillazine.org/Session_Restore

Make sure that you do not use Delete browsing, search and download history on Firefox to clear the "Browsing History" when Firefox is closed because that prevails and prevents Firefox from opening tabs from the previous session.

• https://support.mozilla.com/kb/Clear+Recent+History

-> Tap ALT key or press F10 to show the Menu Bar

-> go to Tools Menu -> Options -> Privacy section -> Firefox will: select "Remember History" -> click OK

Check and tell if its working.

Hi Cor-el and Mha007, thanks for replying.

I tried that and it's still not working. I even uninstalled/re-installed Firefox.

I do appreciate you both taking time to respond. :)

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"

If you use cleanup software like CCleaner then check the settings for the Firefox application.

Thanks, Cor-El.

Yes, that has been de-selected. It's very odd.