You need to restore a JSON backup. Bookmarks &gt; Organize Bookmarks &gt; Import &amp; Backup &gt;

You need to restore a JSON backup.

Bookmarks > Organize Bookmarks > Import & Backup > Restore > Choose File

http://kb.mozillazine.org/Backing_up_and_restoring_bookmarks_-_Firefox

Did you try to delete places.sqlite to make Firefox rebuild the bookmarks from a JSON backup in the bookmarkbackups folder?

http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox