Check your cookie expiration date. When viewing your page, you can call up a list of your site's cookies using either:

• right-click and choose View Page Info > Security > "View Cookies"
• Alt+t (open the classic Tools menu) > Page Info > Security > "View Cookies"
• click the globe or padlock icon > More Information > "View Cookies"

In the dialog that opens, you can select each cookie and inspect the expiration date.

• If they say "At end of session" then there's your trouble.
• If they have a future date, then you would expect that they would either persist or not, the same as other persistent cookies. Unless you use an add-on that selectively preserves some cookies from clearance.
• Even if they persist between sessions, there may be a timeout on the server after which the cookie is invalidated for inactivity.

Make sure that your settings are not to remove cookies when Firefox close.

Also, check the options on your virus scans. They also remove cookies.

I did uninstalled the firefox and installed again, but that still the issue.

Hi cactopia, generally speaking, if you uninstall Firefox without removing your personal data and reinstall Firefox again, you end up with the same settings (bookmarks, options, etc.), so that usually does not change things.

Could you try this test:

Create a new Firefox profile

A new profile will have your system-installed plugins (e.g., Flash) and extensions (e.g., security suite toolbars), but no themes, other extensions, or other customizations. It also should have completely fresh settings databases and a fresh cache folder.

Exit Firefox and start up in the Profile Manager using Start > search box (or Run):

firefox.exe -P

Any time you want to switch profiles, exit Firefox and return to this dialog.

Click the Create Profile button and enter a name like Testing. Do not click the button to change the folder location; the default location is the safest. Then start Firefox in the new profile you created.

Try logging in using the next profile, then exit Firefox and start it again. Do you stay logged in?

To return to your regular profile, start up the Profile Manager again. Please do not delete the Testing profile now. It's a bit too easy to accidentally delete your "real" profile, so I recommend making a backup of all your profiles first in case something were to go wrong. Or just keep it for future testing.

Details like websites remembering you (log you in automatically) are stored in a cookie.

• Create a cookie 'allow' exception to keep such cookies, especially in case of secure websites and when cookies expire when Firefox is closed.
• Options > Privacy > "Use custom settings for history" > Cookies: Exceptions

In case you are using "Clear history when Firefox closes":

• do not clear the Cookies
• do not clear the Site Preferences

• Options > Privacy > Firefox will: "Use custom settings for history": [X] "Clear history when Firefox closes" > Settings
• https://support.mozilla.org/kb/remove-browsing-search-and-download-history

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

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