Tracking "Telling websites you don't want to be tracked" is a little misleading I have found to the majority of consumers. Checking the tracking box, thus opting to tell websites you don't want to be tracked in my opinion is useless, due to the fact that websites are independent and it is only voluntarily if they comply, if at all. They are under no obligation, nor requirement to abide by this even though you have it selected in the browser.

Before attempting to disable third party cookies again, I would suggest first clearing Firefox's cache which can be found via the following KB articles.

See:

Third-party cookies and Firefox tracking protection

How to clear the Firefox cache

If this solved your issue, please select solved & chose the appropriate solution to close this ticket/question posting.

Thanks. I did everything you suggested but it still happens.

You may have an extension that is reverting that setting.

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.org/kb/Safe+Mode

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

See also:

• http://kb.mozillazine.org/Preferences_not_saved
• https://support.mozilla.org/kb/Preferences+are+not+saved

Sounds as if you could have opt-out cookies that are causing this.

These may help -

https://support.mozilla.org/en-US/questions/918421

https://support.mozilla.org/en-US/questions/917566