The most common way of losing bookmarks within Firefox is when the bookmarks toolbar is gone. Usually this means the bookmarks toolbar was accidentally turned off. To turn it back on, click Views > Toolbars > Bookmarks Toolbar > Always show .

Regards, James

this could be a problem with the places.sqlite and favicons.sqlite files in the Firefox profile folder.

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

If errors are reported with "Verify Integrity", close and restart Firefox or reboot and retry.