If you clear history or use Private Browsing, then nothing would have been saved.

If the above does not apply to you, You may have corrupt sessionstore [v56] sessionstore.jsonlz4 file(s). Delete all sessionstore* files and the sessionstore-backups folder.

Type about:support<enter> in the address bar.

Under the page logo on the left side, you will see Application Basics. Under this find Profile Folder. To its right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder

Linux: Under the page logo on the left side, you will see Application Basics. Under this find Profile Directory. To its right press the button Open Directory.

Locate the above file. Then rename or delete it. Restart Firefox.

Don't delete the files if you need to rescue any data from them, just move them out of the profile folder to some location where Firefox doesn't look for them. You can try to read out their contents using this tool: https://www.jeffersonscher.com/res/scrounger.html

Thank you for the response. I never cleared my history and I was not working in a private window. Unfortunately, after following these instructions, the session restore, recently closed tabs, and recently closed windows options are still greyed out. I fear I have lost all of my research work. Maybe I should just turn off the auto updates on Firefox? This is a huge problem for me.

[v57+] Places Maintenance is built into Firefox.

Type about:support<enter> in the address bar.

You will find Places Database near the bottom. Press the Verify Integrity button.

When done, copy and post the results here.

> Task: checkIntegrity + The places.sqlite database is sane + The favicons.sqlite database is sane > Task: invalidateCaches + The caches have been invalidated > Task: checkCoherence + The database is coherent > Task: expire + Database cleaned up > Task: originFrecencyStats + Recalculated origin frecency stats > Task: vacuum + Initial database size is 5120KiB + The database has been vacuumed + Final database size is 5120KiB > Task: stats + Places.sqlite size is 5120KiB + Favicons.sqlite size is 10112KiB + pragma_user_version is 52 + pragma_page_size is 32768 + pragma_cache_size is -2048 + pragma_journal_mode is wal + pragma_synchronous is 1 + History can store a maximum of 112348 unique pages + Table moz_places has 85 records + Table moz_historyvisits has 60 records + Table moz_inputhistory has 0 records + Table moz_hosts has 0 records + Table moz_bookmarks has 47 records + Table moz_bookmarks_deleted has 0 records + Table moz_keywords has 0 records + Table sqlite_sequence has 0 records + Table moz_anno_attributes has 6 records + Table moz_annos has 5 records + Table moz_items_annos has 7 records + Table sqlite_stat1 has 18 records + Table moz_meta has 7 records + Table moz_origins has 1743 records + Index sqlite_autoindex_moz_inputhistory_1 + Index sqlite_autoindex_moz_hosts_1 + Index sqlite_autoindex_moz_bookmarks_deleted_1 + Index sqlite_autoindex_moz_keywords_1 + Index sqlite_autoindex_moz_anno_attributes_1 + Index sqlite_autoindex_moz_origins_1 + Index moz_places_url_hashindex + Index moz_places_hostindex + Index moz_places_visitcount + Index moz_places_frecencyindex + Index moz_places_lastvisitdateindex + Index moz_historyvisits_placedateindex + Index moz_historyvisits_fromindex + Index moz_historyvisits_dateindex + Index moz_bookmarks_itemindex + Index moz_bookmarks_parentindex + Index moz_bookmarks_itemlastmodifiedindex + Index moz_bookmarks_dateaddedindex + Index moz_places_originidindex + Index moz_places_guid_uniqueindex + Index moz_bookmarks_guid_uniqueindex + Index moz_keywords_placepostdata_uniqueindex + Index moz_annos_placeattributeindex + Index moz_items_annos_itemattributeindex > Task: _refreshUI

Good. Nothing wrong with the data. Is the problem still there?

If so; Start Firefox in Safe Mode {web link}

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?