https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save

Note: Some software, like Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

As I mentioned I'd already read this article prior to posting and tried fixes specific to my problem. Those fixes within the article weren't effective in correcting the problem. I don't want to refresh FF and have to again create all custom settings within my profile (visual setup, add-ons and settings within them, etc).

Places Maintenance {web link} Allows to run Maintenance tasks on the database that drives Places, the bookmarks and history module behind Firefox.

Open the Add-ons Manager. Locate the add-on and press the Options button. Then follow the directions.

These can't get your data back, but will help in the future.

These add-ons can be a great help by backing up and restoring Firefox

FEBE (Firefox Environment Backup Extension) {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backups of files that you choose.

OPIE {web link} Import/Export extension preferences

Thank you for these add-ons. I backup all my firefox settings twice monthly when I back up all my data, but these sound quite helpful and I'll explore them. In this particular instance would I reset firefox and then substitute the old profile settings afterward?

FEBE works by backing up what you choose outside of Firefox. It will keep those backups for as long as you choose. I have it set to run each morning, and keep 6 weeks of backups.

If you should lose anything, FEBE can restore it for you.

I run a .bat file to backup any changes twice a month onto an external drive but will definitely explore this when time allows. For the time being, though, this isn't going to solve my inability to change FF options settings. The odd thing is that it had read as I'd checked for custom history settings. Every once in a while for one particular site I need to allow third party cookies, so changed and then couldn't change back after I got off the site. This occurred yesterday. Firefox updated to v. 49.0.2 late evening WED Aug 24, after which this problem occurred. Makes me wonder about that update in relation to the current problem.

Let's try this; Use these links to create a new, blank profile. Do you have the same problem?

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/how-run-firefox-when-profile-missing-inaccessible

You've given me a wealth of information. It will take me a while to find time to print out and read all, decide how to proceed, and implement. (I don't do well with reading documents on the computer, nor with prolonged time at the computer, so it's tricky...)

I'm still not clear on some aspects of how to get the extensions automatically into the new profile rather than having to go through and manually install, configure, etc. Is it the same way as getting bookmarks, etc in there - by coping and pasting into the new profile?

I'll test the new profile first to make sure it holds the setting for History custom settings. I still think this may well have something to do with one of Firefox's updates some point since I last needed to change history settings. Also, I don't see any save button on the options pages any longer. I assume Firefox has changed to a system similar to Chrome where all you do is change the setting without need to confirm change.

When or how soon do you lose the changed third party cookies setting? In other words:

Accept third-party cookies changes from "Never" back to "Always":

• the next time you exit Firefox and start it up again
• at some point during the same session (without exiting Firefox)
• immediately after closing and re-opening the Options page, or it doesn't change successfully at all

It's might be convenient to bookmark about:preferences#privacy if you plan to visit that panel frequently.

Note: If you want to check another way, you can use this method:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste cook and pause while the list is filtered

(3) Double-click the network.cookie.cookieBehavior preference and enter the desired value...

0 => Both first party and third party cookies can be set (default) 1 => Only first party cookies can be set 2 => No cookies can be set 3 => First party cookies can be set; third party cookies can be set only by sites you previously visited directly

If this preference indicates a status of "Locked" that would point toward a file we can help you track down.

I was having the problem when I changed options and re-opened it both within the same session of Firefox and if I closed and re-entered.

After your reply I looked more closely and realized that when history changed from 'custom settings' to 'remember history' , accept third party cookies setting changed from never to always. I changed back to never and the option stuck this time. Have closed and reopened within a session and also exited Firefox and the setting remained once re-opened. I'm very happy it's working properly again. Such a simple and elegant solution. Thank you!