Firebase FCM silent push notifications for iOS
<p>I have a problem with silent notifications on iOS.</p>

<p>When my application is in background, I don't receive silent notification sent by FCM. But if I try to send directly to APNS, the notification is successfully received.</p>

<p>This is the JSON sent to FCM:</p>

<pre><code>{ 
"to" : "&lt;token&gt;",
"priority": "high",
"content_available": true,
"data" : {
  "&lt;key&gt;" : "&lt;string&gt;",
  "&lt;key2&gt;" : "&lt;string&gt;"
}
</code></pre>

<p>}</p>

<p>This is the JSON sent directly to APNS:</p>

<pre><code>{
  "aps": {
    "content-available": 1
  },
  "&lt;key&gt;": "&lt;string&gt;",
  "&lt;key&gt;": "&lt;string&gt;"
}
</code></pre>

<p>I have already tried to remove the "priority" key because I saw someone saying that I shouldn't set the priority if the "content_available" is already set. It didn't work.</p>

<ol>
<li>I have "Push Notifications" enabled in XCode > Capabilities.</li>
<li>I have "Remote notifications" checked in Background Modes in XCode > Capabilities.</li>
<li>The FCM notifications are working fine when app is in foreground and sometimes when the app is in background.</li>
</ol>