I don't use this feature, but I think the following might help.

In a new tab, type or paste about:permissions in the address bar and press Enter. After the page loads, put part of the site's address in the search box at the upper left. Then you should be able to adjust the "Store Passwords" setting for that site.

Does that work?

It didn't seem to. I had to install the add on first. I'll have another go later. It appears that the rule not to offer it after the first time is still in place.

Thanks for suggestion.

I wasn't aware that an add-on was involved. Firefox has its own password saving feature, but certainly there are some others (e.g., LastPass) that you can use instead. If you still have the problem, could you describe in more detail which one you're using?

I was prompted to install in while following your instructions. https://addons.mozilla.org/en-us/firefox/addon/open-aboutpermissions/

Normally as you say, Firefox prompts you to save. It appears that once you have rejected that prompt by x-ing out (ie not clicking one of the 3 choice boxes), it won't ask you again. If you go into Saved Passwords there isn't a facility to add new ones.

I will investigate others as you suggest. I used to use Norton but not any more and I lost all my logins.

Hmmm, I get it now. It seems when you entered about:permissions in the address bar and pressed Enter, instead of opening the about:permissions page immediately it ran a search that led you to the add-ons site. Not sure why that would happen, but hopefully you can access the page by now and "Allow" the site to save passwords.

You can check the password exceptions here:

• Firefox/Tools > Options > Security: Passwords: Exceptions

• https://support.mozilla.org/kb/make-firefox-remember-usernames-and-passwords

• http://kb.mozillazine.org/User_name_and_password_not_remembered