FCM notification title remains "FCM Message"
<p>I'm trying to use the Firebase Cloud Messaging. I send the notifications from a Node.js server to my apps that are registered to the notification system.</p>

<p>My problem is that on Android 5.1 the notification is "FCM Message" even if I setted the title attribute in the nofitification json. It works fine in Android 6.0. I tried to reboot my device as well.</p>

<p><a href="https://i.stack.imgur.com/SFbMg.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/SFbMg.png" alt="enter image description here"></a></p>

<p>And this is the code I use to send the notification:</p>

<pre><code>function sendNotificationToUser(userToken, message, onSuccess) {
  request({
    url: 'https://fcm.googleapis.com/fcm/send',
    method: 'POST',
    headers: {
      'Content-Type' :' application/json',
      'Authorization': 'key='+API_KEY
    },
    body: JSON.stringify({
      notification: {
        "title": 'My App Name',
        "body": message,
        "sound": 'default'
      },
      to : userToken
    })
  }, function(error, response, body) {
    if (error) { console.error(error); }
    else if (response.statusCode &gt;= 400) { 
      console.error('HTTP Error: '+response.statusCode+' - '+response.statusMessage); 
    }
    else {
      onSuccess();
    }
  });
}
</code></pre>

<p>As you can see the notification title I send is "My App Name" but on device it shows "FCM Message".</p>

<p>What do I have to do?!</p>