Получение Mistmatch Senderid в Cordova при отправке push-уведомлений со стороны сервера и Firebase Cloud Messaging

Я пытаюсь выяснить, как отправить push-уведомление, используя Cordova, PHP и Firebase облачные сообщения. Я прочитал почти все доступные учебные пособия и вопросы, но, тем не менее, ни один из них мне не помог.

Вот мой PHP-код:

<?php
// API access key from Google FCM App Console
define('API_ACCESS_KEY', 'AAAABhTlCk4:.....hn7kUNaGnd6ryOTBcFD65axsyOUY');

// generated via the cordova phonegap-plugin-push using "senderID" (found in FCM App Console)
// this was generated from my phone and outputted via a console.log() in the function that calls the plugin
// my phone, using my FCM senderID, to generate the following registrationId
$singleID = $_POST['mobile_ID'];

// prep the bundle
// to see all the options for FCM to/notification payload:
// https://firebase.google.com/docs/cloud-messaging/http-server-ref#notification-payload-support

// 'vibrate' available in GCM, but not in FCM
$fcmMsg = array(
'body' => 'here is a message. message',
'title' => 'This is title #1',
'sound' => "default",
'color' => "#203E78");
// I haven't figured 'color' out yet.
// On one phone 'color' was the background color behind the actual app icon.  (ie Samsung Galaxy S5)
// On another phone, it was the color of the app icon. (ie: LG K20 Plush)

// 'to' => $singleID ;  // expecting a single ID
// 'registration_ids' => $registrationIDs ;  // expects an array of ids
// 'priority' => 'high' ; // options are normal and high, if not set, defaults to high.
$fcmFields = array(
'registration_ids' => array($singleID),
'data' => $fcmMsg
);

$headers = array(
'Authorization: key=' . API_ACCESS_KEY,
'Content-Type: application/json'
);

$ch = curl_init();
curl_setopt( $ch,CURLOPT_URL, 'https://fcm.googleapis.com/fcm/send' );
curl_setopt( $ch,CURLOPT_POST, true );
curl_setopt( $ch,CURLOPT_HTTPHEADER, $headers );
curl_setopt( $ch,CURLOPT_RETURNTRANSFER, true );
curl_setopt( $ch,CURLOPT_SSL_VERIFYPEER, false );
curl_setopt( $ch,CURLOPT_POSTFIELDS, json_encode( $fcmFields ) );
$result = curl_exec($ch );
curl_close( $ch );
echo $result . "\n\n";
?>

Вот мой код JavaScript: https://paste.ee/p/f0zV7

Я получаю ошибку: Файл изображения