I am updating a system that uses the legacy FCM APIs to the new HTTP v1 API: https://firebase.google.com/docs/cloud-messaging/migrate-v1?hl=en&authuser=0. The only functionality we are using is messages sending.

We unfortunately do not have a full test environment set up, so testing is limited to running the server/sender locally and testing with an internal test user who can receive the messages on their device. Based on my understanding, if we can successfully send the message to the new API, everything downstream should continue to work as it always has.

If I send the message below I get a 200 (OK) response, but the user never receives the message. I am passing more data in the “data” element, but removed most of it for clarity. Some notes on trying different variations of what is shown below:

• The auth header is not shown, but I get an unauthorized response if the auth is missing or is expired, so I believe I am successfully getting a token and passing it to the API correctly.
• I am using the target device as the “topic”. The target device Id is known from an unrelated process in the system, and is formatted roughly like this:
  • XXXXXXXXXXXX:YYYYYYYYYYYYYYYYYYYYYYYYYYYY — so a series of letters/numbers, then a colon, then another long series of letters/numbers
  • If I include the whole Id, I get a 400 (Bad Request) error
  • If I only include the part of the Id afterthe colon, I get a 200 (Ok) response
  • I can also change the value after the colon slightly and it will still accept it

Based on the above, I believe the message I am sending passes validation, but fails downstream (invalid deviceId? something else?).

I haven’t been able to find a way to troubleshoot messages that get accepted by Firebase but not delivered. Nothing in the audit logs indicated any kind of error or other message during the times I tried to send.

    {
  "message": {
    "topic": "APA91bHb2-uTYW_VFkZ3LbhKCEWm3kJZmGneDfPss2-T5kkvQquhVqzJdsUfTeB4NRXi3VfSD385_hFebc0AOsIVmEEagyARH2nTZLD_owu7MyqLAhv16ElsdH8wLGDnu742zDcimabc",
    "notification": {
      "body": "Test1.  This is the test message.",
      "title": "TestPlayer Name"
    },
    "data": {
      "body": "Test1.  This is the test message.",
      "title": "TestPlayer Name",
      "vibrate": "1",
      "sound": "1"
    }
  }
}

Does the above message look reasonable? Is the “correct” device Id only the portion of the string after the colon? Is there any way to troubleshoot a message send that is accepted by the endpoint but not delivered to the device?