The bookmarks in the selected HTML file will be added to your Firefox bookmarks within the Bookmarks Menu directory DOES NOT WORK
The current version of FF is a mess. When I installed it, it did not save and reinstall the book marks from the earlier version.
Opaite Mbohovái (1)
Where are you getting that bookmark HTML file from?
Firefox doesn't keep the bookmarks.html file in the Profile folder up-to-date since the Firefox 2 versions; it's only there as a legacy file or as a result of creating a new Profile.
Have you tried restoring a bookmark backup?
https://support.mozilla.org/en-US/kb/Backing-up-restoring-bookmarks
See - Restoring from backups