Deezer API authentication error : I can't make it work

Question

I'm a learning IT student. I'm trying to use the Deezer API to edit playlists on another web site. I cannot get a correct connection to a Deezer account and get this error (with the official Deezer code example):

Warning:
file_get_contents(https://connect.deezer.com/oauth/access_token.php?app_id=...&secret=...&code=...): failed to open stream: HTTP request failed! HTTP/1.0 403 Forbidden in /home///music/index.php on line 44

Code PHP used to create the connection:

<?php
$app_id     = ...;
$app_secret = "...";
$my_url     = "https://music._.fr/index.php";
 
session_start();
$code = $_REQUEST["code"];
 
if(empty($code)){
    $_SESSION['state'] = md5(uniqid(rand(), TRUE)); //CSRF protection
 
    $dialog_url = "https://connect.deezer.com/oauth/auth.php?app_id=".$app_id
        ."&redirect_uri=".urlencode($my_url)."&perms=email,offline_access"
        ."&state=". $_SESSION['state'];
 
    header("Location: ".$dialog_url);
    exit;
 
    }
 
if($_REQUEST['state'] == $_SESSION['state']) {
    $token_url = "https://connect.deezer.com/oauth/access_token.php?app_id="
    .$app_id."&secret="
    .$app_secret."&code=".$code;
 
    $response  = file_get_contents($token_url);
    $params    = null;
    parse_str($response, $params);
    $api_url   = "https://api.deezer.com/user/me?access_token="
            .$params['access_token'];
 
    $user = json_decode(file_get_contents($api_url));
    echo("Hello " . $user->name);
}else{
    echo("The state does not match. You may be a victim of CSRF.");
}
?>

If you could please explain why this code isn't working correctly knowing that I set my Deezer API settings correctly (I think).