I have been trying to make the Mizu VoIPPushGateway work for a while now, but I cannot seem to find what problem it has.

Everything is connected correctly, FCM information is entered correctly, and both test devices/users are listed as push enabled in the server correctly, but whenever I test push notifications sent by the server it never works.

In the logs this message shows:

• the first fcm push notification request failed with reason: 400 400 Bad Request

I have not modified the fcmmessage.txt file either, so it is using the stock configuration.

I could not find anywhere in the documentation if there is a way that we can inspect the JSON file the server is creating to ensure it is using the correct format, so it is a complete mystery as to what the server is trying to send to Firebase.

Is there anyway to fix this problem? The current server tools do not appear to offer any further insight to this issue.