You may have corrupt sessionstore [v56] sessionstore.jsonlz4 file(s). Delete all sessionstore* files and the sessionstore-backups folder.

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

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.

Followed your instructions, and it seemed like it was working correctly, but then it started doing the same thing again. It opened my home pages for two or three sessions, then out of nowhere, it came up with the "unable to restore previous session" error screen, instead of opening my home pages.

Use these links to create a new profile. Use this new profile as is. Is the problem still there?

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

http://kb.mozillazine.org/Profile_folder_-_Firefox#Navigating_to_the_profile_folder

https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

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

Using the new profile as-is seems to work, though it is useless, as I have no access to my bookmarks, log-ins, or password manager add-on.

I open several pages (basically random google searches), and leave them open when I close the browser.

I use the about:profiles to access the original profile when I absolutely need to access my bookmarks etc. (bank account, email, etc.).

Opening the browser with the new profile it always opens just the default new tab, but opening the old profile in a new browser window from about:profiles opens my home pages about 50% of the time, and the "unable to restore previous session" error message the other 50%

Use one of these to close Firefox if you are currently doing that by clicking the close X on the Firefox Title bar.

• "3-bar" menu button -> Exit (Power button)
• Windows: File -> Exit
• Mac: Firefox -> Quit Firefox
• Linux: File -> Quit

I take it the new profile is working without a problem, yes?

When you are ready, we can start moving parts of your old data and Copy it to the new profile.

First; open your file browser to the New profile;

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.

Second, open another file browser to the Old profile. You should see it on the directory "tree" in the first file browser. Right-click on that folder and select Open In New Window.

Warning ! ! Only Copy the files you are told. We will avoid anything that might cause problems. Here is the list of files;

cookies: cookies.sqlite Do not bother. Cookies will be created when you return to the website. However, you will have to log in everywhere. And you may lose any settings that websites store on your computer.

extensions(add-ons, themes): it would be better to download them fresh. If you need to remember what add-ons you had, open the extensions sub-folder and look at the .xpi files

logins.json and key3.db [v58+]key4.db : These are the password files. Copy Both !

persdict.dat : custom dictionary - words you added to the dictionary

mimeTypes.rdf [v55+]handlers.json : What to do with what type of file.

places.sqlite : History and Bookmarks.

prefs.js : Your settings. Note: If you were having problems, this could be contaminated.

cert8.db [v58+]cert9.db and possibly cert_override.txt : Stores all your security certificate settings and any SSL certificates you have imported into Firefox. If removed, the cert8.db, cert9.db file will be replaced.

search.json.mozlz4 : file stores the user-installed search engines that are available in the Firefox v47+

search.sqlite file and searchplugins folder store the search engines that are available in the Firefox Search bar before Firefox v47

Copy these files from the old to the new. You may get a message that the files already exist. Choose to over-write for each file.

I copied most of those (I forgot to copy persdict.dat to the new profile).

Logins.json, key9.db handlers.json places.sqlite prefs.js cert9.db and cert_override.txt search.json.mozlz4

were all copied. The search.sqlite file and searchplugins folder didn't seen to exist. I also re downloaded the lastpass add-on and installed it.

It seemed that it was going to work, for a couple of days, but then this morning, it went back to the "unable to restore previous session" error page when I opened Firefox.

Try what I posted here; https://support.mozilla.org/en-US/questions/1355438#answer-1454179

Tried that, and the first time I launched Firefox afterwards, it went to my home pages as it should. The second time, it opened the one tab I had last been on in the previous session, and the third time, it went back to the "unable to restore previous session" error page again.

Any other suggestions? Or is it time to start looking for a new browser?

Start your Computer in safe mode with network support. Then start Firefox. Try Secure websites. Is the problem still there?

Starting Any Computer In Safe Mode (web link) Free Online Encyclopedia

https://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/

https://www.digitalcitizen.life/4-ways-boot-safe-mode-windows-10/ +++++++++++++++++++++++++++++++++++++++++++++++ If the problem goes away with the computer in Safe Mode, the problem is with one of the other programs on the system.

As a test, disable your protection programs.

If you close down Windows then make sure you give Firefox enough time to finish closing (e.g. one minute) and don't let Windows close Firefox.

I am also having this same issue. Deleting sessionstore didn't do anything, and I cannot boot my work computer in safe mode. This needs a bug fix - there's no reason why the program should be trying to restore a session when the option is unselected.