App (pinned) tabs and Tab Groups (Panorama) are stored as part of the session data [1] in the file sessionstore.js [2] in the Firefox profile folder [3].

Make sure that you do not use "Clear Recent History" 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.org/kb/Clear+Recent+History

• [1] http://kb.mozillazine.org/Session_Restore
• [2] http://kb.mozillazine.org/sessionstore.js
• [3] http://kb.mozillazine.org/Profile_folder_-_Firefox Firefox

It is also possible to use the "Show my windows and tabs from last time" setting, that is usually a more reliable way to restore session data.

• Firefox/Tools > Options > General > Startup: "When Firefox Starts": "Show my windows and tabs from last time"

If you use cleanup software like CCleaner then make sure that Session is unchecked in the settings for the Firefox application.

• App Tab Initializer: https://addons.mozilla.org/firefox/addon/app-tab-initializer/

I very much appreciate your efforts, but none of these suggestions worked. Any other ideas?

(I've removed the solved status as you still have the problem)

Do you see a recent sessionstore.js file in the Firefox Profile Folder?

• http://kb.mozillazine.org/Profile_folder_-_Firefox

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder

It is possible that there is a problem with the files sessionstore.js and sessionstore.bak in the Firefox Profile Folder.

Delete the sessionstore.js [2] file and possible sessionstore-##.js [3] files with a number and sessionstore.bak in the Firefox Profile Folder.

• Help > Troubleshooting Information > Profile Directory: Open Containing Folder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost, so you will have to create them again (make a note or bookmark them).

See also:

• [1] http://kb.mozillazine.org/Session_Restore
• [2] http://kb.mozillazine.org/sessionstore.js
• [3] http://kb.mozillazine.org/Multiple_profile_files_created

Actually, that didn't help but I found a setting that needed to be changed and that worked. I had selected "use custom settings for history" under the privacy tab. When I changed it to "remember history", the tabs remained! I hope this is the way it's supposed to work:-)!

Thank you so much for all your patience and help!!!