In 4.0.1, this function takes two arguments now channelName and name. Not sure what channelName is versus name. Confirmed in game though. /ann is the shortcut (provided by probably many mods) to the now broken API call so /ann won't work until the mods are updated. I think channelName is the primary key of the channel and perhaps name is a friendly name. I can't find anything on this officially so I'm just editing this wiki page to what I found on my own.