why did my attempt to send my email not work status HTTP 303 See Other in codeigniter

why is my attempt to send the email unsuccessful, I can't see the error, all I get is the http status code 303 See More

In my opinion, what I'm doing is in accordance with the official documentation https://codeigniter.com/userguide3/libraries/email.html

the result i expect is an email sent

Can anyone help me? , How can I solve this?

config/email.php

$config['settings'] = array(
'smtp_host'     => 'smtp.mailtrap.io',
'smtp_port'     => '2525',
'smtp_user'     => '9cf16dcde1asdasde5f8',
'smtp_pass'     => '079205e1asdasd26bf43',
'from_email'    => 'no-reply@test.com',
'from_name'     => 'Test',

'protocol'      => 'smtp',
'smtp_crypto'   => 'tls',

'mailtype'      => 'html',
'charset'       => 'utf-8',
'newline'       => "\r\n",
'crlf'          => "\r\n",
);

libraries/Ah_Email.php

<?php defined('BASEPATH') OR exit('No direct script access allowed');

class Ah_Email {
public function __construct()
{
    $CI =& get_instance();
    $CI->load->config('email', true);
    $this->configs = $CI->config->config['email'];

    $CI->load->library('email');
    $this->email = $CI->email;
}

public function send($email_to, $subject, $template, $template_vars = array(), $settings = array())
{
    $settings = array_merge(
        $this->configs['settings'],
        $settings
    );

    $this->email->initialize($settings);


    $this->email->from($settings['from_email'], $settings['from_name']);
    if (isset($settings['send_email']) && $settings['send_email']) {
        $this->email->to($email_to);
    }

    $CI =& get_instance();

    $this->email->subject($subject);
    $this->email->message($CI->load->view('emails/' . $template, $template_vars, true));

    $res = $this->email->send();
    return $res;
}
}

My Controller

public function SendMail() {
    $this->load->library('ah_email', 'ah_email');

    $send = $this->ah_email->send('receiver@gmail.com', 'Informasi Kode OTP Akun Kamu', 'example', array(
        'username'  => 'Ndo Malau',
        'message'   => 'Hello World',
        'mailtype'  => 'text',
    ));

    if($send) {
        $result = redirect(base_url('Systems/Users/index/'), $this->session->set_flashdata('succ_msg', 'success, email has been sending!'));
    } else {
        $result = redirect(base_url('Systems/Users/index/'), $this->session->set_flashdata('err_msg', 'failed, error while email sending'));
    }

    return $result;
}