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.

So "Clear Recent History" is the Ctrl+Shift+Delete one? I tried closing firefox without clearing anything with the ctrl+shift+del pop-up box but all my tabs are forgotten and I am still being brought back to the start page.

It is about the settings here:

• Tools > Options > Privacy > Firefox will: "Use custom settings for history" > Clear history when Firefox closes > Settings

Firefox is permanently set to "Firefox will: Remember history" and I can try changing it to "Use custom settings for history" but it always reverts back to "Remember history" and I don't even have to restart firefox for this setting to reset itself. Every time I go to privacy options, the "Firefox will: (blank)" returns itself to the remember history setting no matter what I do.

If it matters, I can check the settings for what firefox deletes when it closes. All checkboxes are unchecked and . . . . .

In the middle of writing this, firefox just starting remembering the setting I pick in privacy options. Now firefox will use custom settings for history instead of the old "remember history". I'll post this reply now, and perhaps edit it after seeing if things are different now.

"Clear history when firefox closes" -> None of the checkboxes are checked in.

The strange thing is when I go to Show All History (ctrl+shift+h), I can see all my previously viewed pages and open any of them. Restore previous session is always greyed out and I cannot click on it.

Now I'm thinking I should re-install firefox and hope everything starts working fine. I don't mind having to go get all my add-ons again.

Out of taking a complete guess, I disabled the Torbutton add-on and restarted firefox to begin with the add-on no longer functioning. Firefox loads up and all my tabs from last time are forgotten. I open random tabs during this session and close and open firefox. Now all my tabs from last time are showing again.

So I guess Torbutton has more bugs to be worked out and in the meantime I don't have to use it unless there's some kind of emergency that calls for this add-on. I'll take a deeper look into some of the options for torbutton and hopefully I can configure it so it doesn't interfere with my browsing history.

Firefox only shows the "Use custom settings" if at least one history setting is not the default.
If that choice now stays selected then you probably made a change there.

Thanks for spending time to help me figure this out. The problem was being caused by the add-on Torbutton and I found a setting I can change to make things work again. Torbutton Preferences (Options) -> Security Settings -> Startup -> [ ] Tabs loaded in Non-Tor

All I had to do was check in the Tabs loaded in Non-Tor box.

I hope this helps other people who find themselves having this issue.

You're welcome