Recaptcha v3 ของ google return null แก้ไขได้อย่างไรบ้าง

if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['recaptcha_response'])) {

                        // Build POST request:
                        $recaptcha_url = 'https://www.google.com/recaptcha/api/siteverify';
                        $recaptcha_secret = 'XXXXXXXXXXXXXX';
                        $recaptcha_response = $_POST['recaptcha_response'];

                        // Make and decode POST request:
                        $recaptcha = file_get_contents($recaptcha_url . '?secret=' . $recaptcha_secret . '&response=' . $recaptcha_response);
                        $recaptcha = json_decode($recaptcha);

                        // Take action based on the score returned:
                        if ($recaptcha->score >= 0.5) {
                            // Verified - send email
                        } else {
                            // Not verified - show form error
                        }
                    }