I've got PHP Mailer Error: SMTP connect() failed when I use phpmailer?

Question

I've got a problem when I trying to send an email by using PHPMailer, and I'm following this tutorial https://www.000webhost.com/forum/t/how-to-use-phpmailer/134686 because I use 000webhost for my website for free.

PHP code:

<?php
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\Exception;

require $_SERVER['DOCUMENT_ROOT'] . '/mail/Exception.php';
require $_SERVER['DOCUMENT_ROOT'] . '/mail/PHPMailer.php';
require $_SERVER['DOCUMENT_ROOT'] . '/mail/SMTP.php';

$mail = new PHPMailer;
$mail->isSMTP(); 
$mail->SMTPDebug = 2; // 0 = off (for production use) - 1 = client messages - 2 = client and server messages
$mail->Host = "smtp.gmail.com"; // use $mail->Host = gethostbyname('smtp.gmail.com'); // if your network does not support SMTP over IPv6
$mail->Port = 587; // TLS only
$mail->SMTPSecure = 'tls'; // ssl is deprecated
$mail->SMTPAuth = true;
$mail->Username = '[email protected]'; // email
$mail->Password = 'PASSWORD'; // password
$mail->setFrom('[email protected]', 'CKSoftwares System'); // From email and name
$mail->addAddress('[email protected]', 'Mr. Brown'); // to email and name
$mail->Subject = 'PHPMailer GMail SMTP test';
$mail->msgHTML("test body"); //$mail->msgHTML(file_get_contents('contents.html'), __DIR__); //Read an HTML message body from an external file, convert referenced images to embedded,
$mail->AltBody = 'HTML messaging not supported'; // If html emails is not supported by the receiver, show this body
// $mail->addAttachment('images/phpmailer_mini.png'); //Attach an image file
$mail->SMTPOptions = array(
                    'ssl' => array(
                        'verify_peer' => false,
                        'verify_peer_name' => false,
                        'allow_self_signed' => true
                    )
                );
if(!$mail->send()){
    echo "Mailer Error: " . $mail->ErrorInfo;
}else{
    echo "Message sent!";
}

But when I try it exactly, I got an error like this:

2022-03-29 14:56:58 CLIENT -> SERVER: QUIT
2022-03-29 14:56:58 SERVER -> CLIENT: 221 2.0.0 closing connection c27-20020a05620a165b00b0067d32238bc8sm9217183qko.125 - gsmtp
SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting
Mailer Error: SMTP connect() failed. https://github.com/PHPMailer/PHPMailer/wiki/Troubleshooting

And thanks for helping.