TN queue failure notification

I have setup a public queue that deliveries EDI documents to partner.
When this queue fails due to any I like to get notification
I have setup tn.task.notifyFailure = true
as per TN users guide, if the queue fails TN will publish document
I have written the trigger service, but TN does not published tackfailure doc. I dont see any errors in the logs
please provide some guidelines