Getting the "task was cancelled" error

#### Environment

* Operating System version: Windows (Azure instance)
* Firebase SDK version: 2.3.0
* Firebase Product: FirebaseAdmin
* .NET version: 3.1 (net core)

#### Description of the problem:

I'm using FirebaseAdmin (nuget) to send some push notification inside an Azure function. In the local environment it's working perfectly, the SDK is returning the PUSH notifications IDs, but when I run it in a PRIVATE Azure plan, the SDK returns the following error:

"A task was cancelled".

That's all. There's is no other message or stack.

#### Steps to reproduce:
I don't know. I think this is a firewall blocking but I need more logs from the SDK to be completely sure.

#### Relevant Code:

```
try
{

logger.LogInformation("NS. Step 1. Firebase configuration credentials: " + _messageConfig);

var fcm = FirebaseAdmin.Messaging.FirebaseMessaging.GetMessaging(app);

logger.LogInformation("NS. Step 2. Firebase Messaging instance creates: " + _messageConfig);

Message message = new Message()
{
Data = new Dictionary
{
{"OrderNbr",pushNotification.OrderNbr},
{"CdNbr", pushNotification.CdNbr.ToString()},
{"StoreNbr",pushNotification.StoreNbr.ToString()},
{"type",pushNotification.type.ToString()}

},
Notification = new FirebaseAdmin.Messaging.Notification
{

ImageUrl = "https://firebasestorage.googleapis.com/v0/b/lookapp-dev-77465.appspot.com/o/LOOK_APP_little.jpg?alt=media&token=3eadd967-f158-4ad8-8469-62a1fad91311",
Title = pushNotification.title,
Body = pushNotification.description
},
Token = String.IsNullOrEmpty(pushNotification.deviceTokenAndroid) ? pushNotification.deviceTokenIOS : pushNotification.deviceTokenAndroid
};

logger.LogInformation("NS. Step 3. Message created, sending....");

var result = fcm.SendAsync(message);

logger.LogInformation("NS. Step 4. Result from firebase (notification id):" + result.Result);
return result.Id;

}
catch (Exception ex)
{
logger.LogError(ex, $"Error sending firebase message");
throw;
}
```

#### Notes

I just want to know what kind of issue produces this error.
Should I manage the firewall to enable any URL?

Thanks in advance