Chrome extension not receiving Firebase Cloud Messages - google-chrome

Question

Something really weird is happening with me. Yesterday atfernoon I realized my chrome extension wasn't receiving Firebase Cloud Messages sent by my server. I've tried to create a new Chrome Extension with nothing more than the GCM API and a simple server page with the message sender, but it still not working.
Suddenly it started working again and I received ALL the messages that I sent in that period!! I thought it was a server issue and ok. Today in the morning it was working perfectly. BUT AGAIN, in the afternoon, it stopped! I don't know what to do, I've been using Chrome extension with the GCM API for months and it have never happened before.
My extension:
manifest.json
{
"name": "__MSG_myextension__",
"version": "1.3",
"icons": {
"128": "images/my-icon.png"
},
"permissions": [
"background",
"gcm",
"storage"
],
"background": {
"scripts": ["background.js"]
},
"manifest_version": 2,
"default_locale" : "en"
}
background.js (yes I copied from here)
function registerCallback(registrationId) {
console.log(registrationId);
if (chrome.runtime.lastError) {
console.log(chrome.runtime.lastError);
return;
}
}
var senderIds = ["MY-SENDER-ID"];
chrome.gcm.register(senderIds, registerCallback);
chrome.gcm.onMessage.addListener(function(message) {
console.log(message);
});
My server:
$registration_id = '...';
$key = '...';
$message = '{"collapse_key":"'.time().'","data":{"message":"hello world"},"priority":"high","registration_ids":["'.$registration_id.'"]}';
$headers = array(
'Content-Type: application/json; charset=UTF-8',
'Authorization:key=' . $key );
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://fcm.googleapis.com/fcm/send");
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, true);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_ENCODING, 'UTF-8');
curl_setopt($ch, CURLOPT_POSTFIELDS, $message);
$result = curl_exec($ch);
var_dump($result);
As a result from my curl, I'm getting always success.
I'm pretty sure I'm sending the message to the right registration ID.
Can somebody help me??