Oracle Notification Troubleshooting in 3 steps

From the failed notification, determine the notification ID.
Step 1:
Use the notification ID to determine the context under which the API was called

select substr(notification_id, 1, 12) nid, substr(status, 1, 8) status, substr(recipient_role, 1, 20) recipient, substr(message_name, 1, 25) message, substr(mail_status, 1, 8) mstatus,
substr(message_type, 1, 25) mtype, substr(context, 1, 25) context, BEGIN_DATE, END_DATE, DUE_DATE
from wf_notifications
where notification_id= &1;

Step 2:
Use the recipient (recipient_role) to check the user's notification preference for an email address and that it is a valid one.

set linesize 155;
set pagesize 200;
set verify off;
col name format a20;
col display_name format a40;
col email_address format a50;
col status format a8;
col notification_preference format a25;
col orig_system format a15;
col orig_system_id format 999999999999;
col start_date format a12;
col expiration_date format a16;
select name, display_name, email_address, status, notification_preference, orig_system,
orig_system_id, start_date, expiration_date
from wf_roles
where name like %a%;

Step 3:

From the context, determine the item type an item key. The context has the format:


ITEM_TYPE:ITEM_KEY:ACTIVITY_ID
Use wfstat.sql or wfstatus.sql to determine the value of the DOCUMENT Item Attribute of the failed instance. The item type and item key were found in the context column.

sqlplus apps/apps @$FND_TOP/sql/wfstat.sql item_type item_key