There have been reports of the display not updating until the user mouses over the plugin to show the tooltip. I've seen this happen once myself, when a friend logged into another toon. At the moment I suspect it may be a Battle.Net API bug (like so many things recently), as I didn't get a message in the chat window either informing me that they logged in, but this needs to be investigated.

Fixed by 1e7e9b5.