email Notifications not reaching users

Hi,
Workflow notification corrosponding to  'PORCPT' are not reaching users.
I tried to follow note 831982.1 in metalink and made  the below query  by hard coding it for some users that usually receive notifications  and it returned 0 rows.

select recipient_role,notification_id,status,mail_status ,begin_date
from applsys.wf_notifications where recipient_role in( 'MCKENZIEJ','MCCUBBINEE','VIRNAUI','DWYERN')
AND trunc(begin_date)<trunc(sysdate)
and trunc(begin_date)>trunc(sysdate-45)
AND mail_status in ('MAIL','INVALID')
and status in ('OPEN','CANCELED')
order by trunc(Begin_date) desc;

I see most of the rows have mail_status as  send in wf_notifications