Hello
I have an apex application with custom authentication but using the builtin authorization schemes.

I also have a user with the Administrator Role.

This user is in my table USERS, and APEX tables APEX_APPL_ACL_USERS and APEX_APPL_ACL_USER_ROLES.
My custom authentication is working. I can login and logout.
The processes on my user_form, add user and role, edit user and role and delete user and role are also working fine. Here is an example of one of the codes:
begin
APEX_CUSTOM_AUTH.SET_USER(:P7_USER_NAME);
APEX_ACL.ADD_USER_ROLE (
p_application_id => 100,
p_user_name => :P7_USER_NAME,
p_role_static_id => :P7_USER_ROLE
);
end;
Now the issue is, when I try to access a page configured as => Security => Administration Rights, I get the error

I am new to Apex, trying to learn from youtube and documentation. I have been over this for one week. I cannot fix this alone.
Would anyone help me?