What do the logs say? In development mode, session sharing should output something that starts with
[session-sharing] Processing login for uid ...If you don't see that, then the cookie didn't verify, potentially.
Also, if the unique ID you passed in no longer resolves to an active user, the login might also fail. Check the appId:uid (or replace appId as needed) sorted set to see if there is an outdated entry in there.
