After adding a user (Manual) I can't send an email

When I manually add a user to my simple script with php 7.4 and using mysqli, no email is sent to him, why?

<?php   

  require_once 'core.php';
  include ('phpmail/class.phpmailer.php');
  include ('phpmail/class.smtp.php');

$valid['success'] = array('success' => false, 'messages' => array());
    
$Mesagetopic = "Welcome my area..";   
$Mailsendto = $uemail;

if($_POST) {    

  $userName         = $_POST['userName'];
  $upassword        = md5($_POST['upassword']);
  $uemail       = $_POST['uemail'];

        
                $sql = "INSERT INTO users (username, password,email) 
                VALUES ('$userName', '$upassword' , '$uemail')";
                $basarili = $valid['success'] = true;
                if($connect->query($sql) === TRUE) {


    $mail = new PHPMailer();
    $mail->IsSMTP();
    $mail->SMTPAuth = true;
    $mail->Host = 'smtp.yandex.com'; //Smtp Host
    $mail->SMTPSecure = 'ssl';  
    $mail->Port = 465;  
    $mail->Username = "axxxxx@yandex.com"; 
    $mail->Password = "xxxxxx"; 
    $mail->SetFrom('axxxxxx@yandex.com', 'Hello'); 
    $mail->AddAddress("$Mailsendto", 'Oliver T.'); 
    $mail->CharSet = 'UTF-8'; 
    $mail->Subject = "Hey Read Me>>"; 
    $mail->MsgHTML("$Mesagetopic); 
  
                    $valid['success'] = true;
                    $valid['messages'] = "User Added";  
                }           

                else {
                    $valid['success'] = false;
                    $valid['messages'] = "Error! No Add";
                }

                // /else    
    } // if in_array    

    $connect->close();
    echo json_encode($valid);
 

What could cause this error, e-mail why not go after manual record insertion? There is no attribute error in my html codes that submit the form

source https://stackoverflow.com/questions/76596193/after-adding-a-user-manual-i-cant-send-an-email