Add-on signing isn't currently turned on, so it shouldn't be affecting any of your add-ons (BTW, your Firefox is out of date, please update to Firefox 42). Norton has been having their own problems with their extensions, which are entirely their own fault (they delayed months to ensure their addons were compatible despite repeated warnings).

You should cease using Norton extensions if at all possible, they have not proven themselves responsible enough to be trust worthy and their extensions have known issues and duplicate features already in Firefox. I'd suggest using the Firefox password manager. Password Manager - Remember, delete and edit logins and passwords in Firefox

If you have the November 5th update, then unfortunately you are in limbo when it comes to using your password "vault"; most other features should be working. It may be some time before Norton finishes its compatibility fixes. See:

• https://community.norton.com/en/blogs/product-update-announcements/firefox-41-and-42-limited-support-norton-toolbar

• https://support.norton.com/sp/en/us/norton-identity-safe/current/solutions/v115161915_EndUserProfile_en_us

• http://community.norton.com/en/forums/firefox-42-and-norton-toolbar

As you can imagine, since this is security software, none of us is going to freelance with suggested hacks or recommend downloading old versions from random websites. If you prefer to stick with this password manager, you can use Norton's forums to help keep the pressure on.