ion auth won't redirect after registered

I am using ion auth for my CI authentication. I got a problem with auto login after registered. I got no problem with the register, all data are inserted and i can get to login with my login form. But it won't redirect to the home page after a user registered.

below is my code. Can anyone take a look?

if ( $this->form_validation->run() == TRUE )
        {   
            //if form validation not false, password var
            $username = $this->input->post('email');
            $password = $this->input->post('password');
            $email = $this->input->post('email');
            $additional_data = array(
                                        'first_name' => $this->input->post('first_name'),
                                        'last_name' => $this->input->post('last_name'),
                                    );
        }

        if ($this->form_validation->run() == TRUE && $this->ion_auth->register($username, $password, $email, $additional_data))
        { 
            //check to see if we are creating the user
            //redirect them back to the home page
            $this->session->set_flashdata('msg', "User Created");
            redirect("auth/home", 'refresh');
        }
        else
        {
            $this->session->set_flashdata('msg', validation_errors('<div>','</div>'));
            redirect('auth/index','refresh');
        }

It is because the user is "registered" but they are not "logged in". You need to manually log them in, after the register, but before you redirect.

        if ($this->form_validation->run() == TRUE && $this->ion_auth->register($username, $password, $email, $additional_data))
         {              
              //check to see if we are creating the user             
              //redirect them back to the home page            
               $this->session->set_flashdata('msg', "User Created");   
              // ***DO MANUAL LOGIN HERE WITH ION_AUTH***
              redirect("auth/home", 'refresh');     
          }