I found out if you logged out and closed FF and reopened and login back to the site will usually work for it to ask you to login again. Otherwise go to you password settings and uncheck or remove your no there to let it save again.

Try Clear your Cache and Remove the Cookies for that site.

Clearing cache and cookies did not work.

How do I "go to you password settings and uncheck or remove your no there to let it save again"? I've never seen anything like that.

Could you check here:

• Windows: "3-bar" menu button (or Tools menu) > Options
• Mac: "3-bar" menu button (or Firefox menu) > Preferences
• Linux: "3-bar" menu button (or Edit menu) > Preferences
• Any system: type or paste about:preferences into the address bar and press Enter/Return to load it

In the left column, click Privacy & Security

Then on the right side, next to "Ask to save logins and passwords for websites", click the Exceptions button to see whether the site is listed there. If so, you can click it to select it, click the Remove Site button, then click the Save Changes button at the lower right. (If you don't see the Save Changes button, try enlarging the dialog using the "grippy" in the lower right corner.)

Success?

See also the "To tell Firefox to never remember usernames and passwords for the current website," section:

• https://support.mozilla.org/en-US/kb/password-manager-remember-delete-change-passwords