In sys.transmission_queue the only information I'm given is "One or more messages could not be delivered to the local service targeted by this dialog."
If I re-enable one of the problem queues (there are five) and leave Activation set to OFF, the queue fills up with its messages. If I then run the Activation SP, I process the messages correctly and without issue. But as soon as I turn activation ON, if there are ANY messages in the queue, the queues will disable themselves again.
I'm completely lost. Does anyone know how I can troubleshoot this?