php - Call to a member function execute() on boolean in

My html :

 

        Email : 
        Message : 
                
    

My rent.php file :

 require_once 'login.php';
   $conn = new mysqli($hn, $un, $pw, $db);
   if ($conn->connect_error) {
    die($conn->connect_error);
}
    $query = "SET NAMES utf8";
    $result = $conn->query($query);
    if (!$result) {
        die($conn->error);
    }
    $req = $conn->prepare('INSET INTO renter (email, msg_text) VALUES(?, ?)');
    $req->execute(array($_POST['email'], $_POST['msg_text']));
    header('Location: menu.php');

My error when I try to submit, is : Fatal error: Call to a member function execute() on boolean in C:...\rent.php on line 18

email, msg_text are in varchar type