Follow this answer thread. This might be helpful.

https://support.mozilla.org/en-US/questions/971923?esab=a&s=firefox+deleting+session+cookies&r=9&as=s

Thank you.

I first had an issue where cookies wouldn't save after closing Firefox no matter what settings I used, so I read that thread and did manage to fix it by deleting all cookies manually, but the issue remains where it won't save my session cookies.

Thanks.

Try this:

Go to "Tools" >> "Options" >> "Privacy" , in the option " The Firefox must:" set "Never memorize", click on OK

Go to your address bar and type "about:config", in the search bar, type "browser.privatebrowsing.autostart" will apper a single option change this optionto true.

Do you use any cookie or privacy related extensions (or external software) that might be altering Firefox's normal behavior?

Have you noticed anything else going wrong with the session restore feature that might suggest the file has become corrupted in some manner?

Actually, you have Firefox set to clear cookies on shutdown. Why did that combination ever work?!

Apparently the fact that cookies in your session store file were not cleared was a bug that was fixed, perhaps accidentally, in Firefox 26. (Based on the last comment here: 662485 – Clear history when Firefox closes: cookies, doesn't clear session cookies in Firefox 4+)

You may need to find a new cookie management strategy...

Wow, nice researching, jscher2000.

Well, this page seems to imply that there's a way to have Firefox only save the cookies of your session, otherwise why would they have that feature at all? There would just be an option to delete all cookies on close or none of them, not a session specific retention of data.

Although I suppose it's possible that browser.sessionstore.privacy_level just doesn't work as it's fully intended, because as I mentioned, it does maintain my logins for some sites—this one, for example—when I have 'keep until' set to 'they expire' and 'cookies' checked in the clear history settings. My sense is that this is indeed the thrust of the issue.

Thanks.

Everyone's needs are different, but my strategy is to set "session only" as the default for all cookies, and then NOT clear cookies at shutdown. There are some sites where I want to stay logged in, so I create exceptions for those sites allowing them to create persistent cookies. You might not want to create any exceptions, so it should be a fairly simple fix for you.

(1) Set cookie lifetime to session only

orange Firefox button (or Tools menu) > Options > Privacy

Set "Keep Until: I close Firefox"

(2) Do not clear cookies at shutdown

orange Firefox button (or Tools menu) > Options > Privacy > "Settings" button

That solution seems fine, but I can't seem to get exceptions to save. I even tried renaming the places, cookies, and permissions sqlite files thinking it was a corruption, but it still wouldn't save my exceptions. Whenever I close Firefox, they disappear from the exceptions list, and there's no mention of the exception in about:permissions. When I rename all the sqlite files, I can get them to appear in about:permissions after a close, but 'Set Cookies' changes back to 'Allow for Session' rather than 'Allow'. Very bizarre.

Thanks.

Do not clear the Site Preferences as well.

Note that clearing "Site Preferences" clears all exceptions for cookies, images, pop-up windows, software installation, and passwords.

Clearing cookies will remove all specified (selected) cookies including cookies with an allow exception that you would like to keep.

Ah, that was indeed the issue.

Thanks for the help, jscher2000 and cor-el. Looks like that'll work just fine for my needs.  :-)