Need help with Oracle OCI Advanced Queue!

Hello, I am working with Oracle9i Enterprise edition, and I've created the queue, queue-table, stored-proc and trigger, so that my OCI program will be notified when someone logged on.

However, my callback function was never called, even though everytime a user logs on, a new entry is added to the queue and queue-table, what gives??

Here is part of my OCI code(where scott.LOGON is my advanced-queue name):

	subscrhp = (OCISubscription*)0;
	(void) OCIHandleAlloc((dvoid*)envhp, (dvoid**)&subscrhp, 
		 (ub4) OCI_HTYPE_SUBSCRIPTION, (size_t)0, (dvoid**)0);

	(void) OCIAttrSet((dvoid*)subscrhp, (ub4) OCI_HTYPE_SUBSCRIPTION,


		  (dvoid*)"scott.LOGON",

		  (ub4) strlen("scott.LOGON"),


		  (ub4) OCI_ATTR_SUBSCR_NAME, errhp);



	(void) OCIAttrSet((dvoid*)subscrhp, (ub4) OCI_HTYPE_SUBSCRIPTION,


		  (dvoid*)OCI_SUBSCR_PROTO_OCI, (ub4)0,


		  (ub4) OCI_ATTR_SUBSCR_RECPT, errhp);



	(void) OCIAttrSet((dvoid*)subscrhp, (ub4) OCI_HTYPE_SUBSCRIPTION,


		  (dvoid*)notifySnoop, (ub4)0,


		  (ub4) OCI_ATTR_SUBSCR_CALLBACK, errhp);



	(void) OCIAttrSet((dvoid*)subscrhp, (ub4) OCI_HTYPE_SUBSCRIPTION,


		  (dvoid*)&ctx, (ub4)sizeof(ctx),


		  (ub4) OCI_ATTR_SUBSCR_CTX, errhp);



	(void) OCIAttrSet((dvoid*)subscrhp, (ub4) OCI_HTYPE_SUBSCRIPTION,


		  (dvoid*)&mynamespace, (ub4)0,


		  (ub4) OCI_ATTR_SUBSCR_NAMESPACE, errhp);



      thanks,

      Tony