A couple of times I've had a duty briefly come up, cancel and then instead of returning me to the queue, I get the message "Unable to register. Duty registration has ended." and I'm no longer in the queue. One time I saw it happen in front of me, another time it just happened while I'd left it to do other stuff, and came back to find the message in my chat log.
It's not the same thing as when you actively fail to press the Commence button and it tells you you've been penalised for not joining.
It may have only happened with my character on Sophia, and/or may have only been for PVP duties, but I'm not certain on either of those counts.
Has anyone else seen it happen, or know what causes it?