Unable to successfully send android notification

We are trying to send a push notification on android device using GCM/FCM with the latest Notification-Hubs-java-sdk version (1.0.4).

We wrote the same code in dotnet and we can successully send a notification. Using the java sdk we see that the notification are received on notification hub but they never pass to successfull status on dashboard.

Watching the situation on firebase with the java code none of the notification are delivered to the account. Instead, the same hub, used by dotnet delivered notification successfully.

Working Dotnet code
```c#
String TOKEN = "XXXXX";
String CONNECTION_STRING = "Endpoint=sb://joinon-notificationhub-dev.servicebus.windows.net/;SharedAccessKeyName=joinon-notificationhub-dev;SharedAccessKey=YYYYY";
String HUB_NAME = "joinon-notificationhub-dev";
String BODY = "{\"data\":{\"title\": \"maco: TESTME\",\"body\" : \"Nessuna perdita d’acqua nella stanza sensori.\", \"icon\": \"notification/water_off\"}, \"notification\":{\"title\": \"maco: Nessun allarme perdita acqua rilevato\",\"body\" : \"Nessuna perdita d’acqua nella stanza sensori.\"}}";

String installationId = "installationIdTest";
NotificationHubClient _notificationHub = NotificationHubClient.CreateClientFromConnectionString(CONNECTION_STRING, HUB_NAME);

Installation installation = new Installation();
installation.InstallationId = installationId;
installation.PushChannel = TOKEN;
installation.Platform = NotificationPlatform.Fcm;
await _notificationHub.CreateOrUpdateInstallationAsync(installation);

Task outconme = _notificationHub.SendFcmNativeNotificationAsync(BODY, "$InstallationId:{" + installationId + "}", CancellationToken.None);

await _notificationHub.DeleteInstallationAsync(installation.InstallationId);
```

NOT Working Java code
```java
String TOKEN = "XXXX";
String CONNECTION_STRING = "Endpoint=sb://joinon-notificationhub-dev.servicebus.windows.net/;SharedAccessKeyName=joinon-notificationhub-dev;SharedAccessKey=YYYYY";
String HUB_NAME = "joinon-notificationhub-dev";
String BODY = "{\"data\":{\"title\": \"maco: TESTME\",\"body\" : \"Nessuna perdita d’acqua nella stanza sensori.\", \"icon\": \"notification/water_off\"}, \"notification\":{\"title\": \"maco: Nessun allarme perdita acqua rilevato\",\"body\" : \"Nessuna perdita d’acqua nella stanza sensori.\"}}";

NotificationHub notificationHub = new NotificationHub(CONNECTION_STRING, HUB_NAME);

String installationId = "installationIdTest";
Installation installation = new Installation(UUID.randomUUID().toString(), NotificationPlatform.Gcm, TOKEN);

notificationHub.createOrUpdateInstallation(installation);
Notification n = Notification.createFcmNotification(BODY);
NotificationOutcome outcome = notificationHub.sendNotification(n, "$InstallationId:{" + installationId + "}");

notificationHub.deleteInstallation(installationId);
```