Hi, easy things first. So try closing and restarting Firefox (3-bar menu > Exit Firefox, in bottom right corner). If that doesn't help, you can try this: Open bookmarks > Show All Bookmarks > Import and Backup > Restore, and see if you have a backup there.

If not, it gets a bit more complex, so please see -

• Profiles - Where Firefox stores your bookmarks, passwords and other user data.

• Recovering important data from an old profile.

If your question is resolved by this or another answer, please take a minute to let us know. Thank you.

You can check for problems with the places.sqlite database file in the Firefox profile folder.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox
• https://support.mozilla.org/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

• Places Maintenance: https://addons.mozilla.org/firefox/addon/places-maintenance/

You can try to restore the bookmarks from a compressed .jsonlz4 backup in the bookmarkbackups folder.

• Bookmarks > Show All Bookmarks > Import & Backup > Restore

• https://support.mozilla.org/kb/restore-bookmarks-from-backup-or-move-them

It is possible that you did refresh (reset) Firefox and have created a new profile.

• https://support.mozilla.org/kb/refresh-firefox-reset-add-ons-and-settings

This could happen if Firefox reported that it was starting slowly.

When you reset/refresh Firefox then a new profile is created and some personal data (bookmarks, history, cookies, passwords, form data) is automatically imported. The current profile folder will be moved to an "Old Firefox Data" folder on the desktop. Installed extensions and other customizations (toolbars, prefs) that you have made are lost and need to be redone.

It is possible to recover data from the old profile, but be cautious not to copy corrupted files to avoid carrying over problems.