Oracle session trigger doesn't seem to execute properly

Hi Experts,

     I created a trigger to ALTER the session when a particular user logs on and I don't think that the trigger is being triggered.  I created the below trigger under the SYSTEM schema and it didn't work, so then I created it under the user's schema and it didn't work either.  I don't think that the trigger is getting executed when the user starts a session.  I say that because if I run the same exact code using the same user during a SQL*PLUS session, it works great!  What I mean is that If I connect as the user via SQL*PLUS and I alter my session I am able to verify that the session was altered.  However, after creating the trigger, if I connect via SQL*PLUS as the same user, not alter my session (trying to rely on the trigger to alter the session) I am not able to verify that the session was altered.  What am I doing wrong?  Again, I have tried creating the trigger under both the SYSTEM and the user's schema.

Here's the trigger:

create or replace
TRIGGER "ACTIVETRACK"."ON_LOGON_ACTIVETRACK"
AFTER LOGON ON DATABASE
WHEN ( USER = 'ACTIVETRACK' )
BEGIN
execute immediate 'ALTER SESSION set nls_sort=BINARY_CI scope BOTH';
execute immediate 'ALTER SESSION set nls_comp=ansi scope BOTH';
EXCEPTION
WHEN OTHERS THEN
NULL;
END;

Select allOpen in new window

Thanks!