In Administration -> Online Users, there used to be a list of online users who we can "Send Message". Now suddenly the list disappear. How do I get it back?
Isn't it merely hidden by personalization?
I don't think so, coz it happened to all users, not just some.
I would review (and debug if needed) the logic showing the list. Unfortunately I don't remember anymore how it used to work in Axapta 3.0, therefore it's up to you.