I spent an hour in chat today (17 Jan 2016) with Norton support, and got this understanding from them. I'm posting this so others have quicker access to this information.
Previously posted: (I) Mozilla’s platform changes in FF41 drove widespread recoding requirements in addons. e.g.: https://community.norton.com/forums/firefox-41-and-norton-toolbar-compatibility
Update: (II) Reportedly, Mozilla is changing their position towards addons, becoming less open to them. These two factors (I & II) led Mozilla to struggle with a load of addon approvals testing. This bogged down their approval of Norton’s password vault ... for four months so far, and counting. (There are no claims of anticompetitive strategies, e.g., driving us away from Norton’s password manager and to Mozilla’s.) Norton believes the fundamentals driving this delay of Mozilla’s approval of their addon, and Norton's recoding in Norton 22.5 (current) and 22.6 (coming), will make this massive approval delay a one-time thing -- i.e., it should not recur as Mozilla releases their (widely-hated) monthly version change. Norton can offer no E.T.A. for a resolution, since it is solely in Mozilla’s control. Meanwhile, users have two workarounds: (1) Manually cut-&-paste passwords. [Open Norton’s password vault in the desktop app for Norton, manually search for the password of interest, and manually copy it from Norton, and past it into the webpage.] Or, (2) Use another major browser -- like Chrome or IE -- for any security-sensitive browsing.