If Firefox starts up without your bookmarks, passwords, saved tabs and other settings, check whether your data is available in a different profile. This can happen because Firefox creates a dedicated profile for each installation of Firefox.
To recover your Firefox data and settings from another profile:
Type about:profiles into the Firefox address bar and press the EnterReturn key. This will open the About Profiles page.
This page should list at least one profile and could list many. The profile that Firefox is currently using will have this under the profile name: This is the profile in use and it cannot be deleted.
If you have another profile listed on this page, it may contain your missing profile data. You can click thebutton to open another Firefox window using that profile. If the other profile doesn't contain your missing data, simply close that new window. If it does contain the missing data, you can set it as the profile that Firefox will open by default. Click the button for that profile, and Firefox will use it automatically the next time you open Firefox.
If you can't recover your missing data this way, you may be able to manually recover data from another profile. See the Recovering important data from an old profile article for details.
For more information about managing Firefox profiles, see the Profile Manager article.