Hello! App Tabs are stored in files which are associated with your history and session. When you clear your history, you are preventing Firefox from restoring the current tabs you're in. If this issue is happening every time you start up Firefox:

• Check if Firefox isn't set to clear history automatically when closing the browser:

Read the "How do I make Firefox clear my history automatically?" in the Delete browsing, search and download history on Firefox article, and deactivate this feature by selecting "Remember history". Alternatively, you may also set custom settings, and deselect the option "Clear history when Firefox closes".

• Check if you are in Private Mode. Private Mode clears automatically your browsing session, so your tabs will not open in the next session.

Thank you, your reply is very helpful. Unfortunately it is more important to me to use the private browsing and clear history functions than App Tabs. Thank you for posting this reply as I am sure others will have this question as well.

You're welcome :-)