You can check for problems with the places.sqlite database (bookmarks and history) in the Firefox profile folder.

• use "Verify Integrity" on the "Help -> Troubleshooting Information" (about:support) page

See also:

• http://kb.mozillazine.org/Locked_or_damaged_places.sqlite
• https://support.mozilla.org/en-US/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

If "Verify Integrity" on the "Help -> Troubleshooting Information" (about:support) page cannot repair places.sqlite then remove all places.sqlite files Firefox profile folder. Firefox will rebuild places.sqlite and restore the bookmarks from the most recent JSON backup in the bookmarkbackups folder.

• keep a backup copy of places.sqlite in case a new places.sqlite database has to be created
• http://kb.mozillazine.org/Unable_to_process_the_backup_file_-_Firefox

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

your answer was not helpful. please look my link picture. I can see old bookmark in only this section I can't understand this situation :(

https://imgur.com/X5twqhw

What you see in the Library Bookmarks drop-down list under Recently Bookmarked is the result of a query and not a bookmarks folder.

If you do not see any bookmarks in the Bookmarks Manager (Library) then you likely have a problem with places.sqlite like I posted above, especially if you have a problem with restoring a JSON backup from the bookmarkbackups folder.

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

The name of an automatically created JSON bookmarks backup in the bookmarkbackups folder includes a total item count (folders and separators included) and an hash value to prevent saving the same backup more than once.

• bookmarks-YYYY-MM-DD_<item count>_<hash>.jsonlz4.

If I send you a my jsonlz4 file, can you check & restore it?

https://drive.google.com/open?id=16VceqdTPA-hr4_QJl6mKVwedQ7QhhI4s

You can use this page to convert the compressed file to an HTML-format file you could import. If you want to try that:

https://www.jeffersonscher.com/res/bookbackreader.html

Solved!!! Thank you very much for your help~!!!!!! ^0^

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