Zoning into a zone that did not start up correctly.
Your health is correct but everyone else including NPCs health bars do not move. Your group member's mana or endurance bars do not even display.
This popped out of the blue for me. the past 5 days it has happened in at least 4 zones. The zone needs to remain inactive for a period of time until it basically shuts down and when someone zones in again it will restart.
I just wanted to point this out, in case you all made a change to the server recently.