Function does not return any data

Hi Experts,
here is the function that I am having a problem with. It doesn't return any data. However, when I run the select statement from SQL*PLUS it brings data back. what is the problem?
Please help!
CREATE OR REPLACE FUNCTION get_usage_rep(p_start_date date, p_end_date date)
  RETURN sys_refcursor AS
  v_report            sys_refcursor;
  whereclause         varchar2(3200):='and  u.affiliate_id in  (select aff_id from ultra_affiliate)';  
 
begin

open v_report for
  'select distinct initcap( u.first_name) || initcap( u.last_name )full_name '
     || chr (10)
     ||' from ubcsecurity.user_session s,cod_security_vw u, ultra_affiliate ua '
     || chr (10)
     ||' where s.user_name      = u.user_name '
     || chr (10)    
     ||' and   ua.aff_id = u.affiliate_id '
     || chr (10)    
     ||' and   s.login >= '''|| p_start_date|| ''' and   s.login <= '''|| p_end_date|| ''' '
     || chr (10)
     || whereclause
     || chr (10)
     || ' group by initcap( u.first_name) || initcap( u.last_name ) '
     || chr(10)
     ||' order by initcap( u.first_name) || initcap( u.last_name ) ';
   return v_report;
end;