Sending FCM notification with Fids Return NotRegistered

[FabienBounoir]

Environment

• FirebaseAdmin: 3.6.0
• .NET: (your version)
• Platform: iOS
• FCM HTTP v1 (through Firebase Admin SDK)

Description

I'm trying to migrate from registration tokens to FIDs as recommended by the SDK.

When sending a notification to an Apple device using the Fid property of Message, the Admin SDK always returns a FirebaseMessagingException with the error NotRegistered.

However, using the exact same FID from the Firebase Console ("Send test message"), the notification is delivered successfully to the device.

This suggests either:

• the .NET Admin SDK is not sending the request correctly when using Message.Fid, or
• there is a backend/API discrepancy between the Admin SDK and the Firebase Console.

Code

var message = new Message
{
    Fid = fid,
    Notification = new Notification
    {
        Title = "Test",
        Body = "Hello"
    }
};

await FirebaseMessaging.DefaultInstance.SendAsync(message);

[yvonnep165]

Hi @FabienBounoir ,

Could you please confirm if you have updated your client app to properly register and retrieve the Firebase Installation ID (FID)?
Please verify your client implementation against this guide to ensure the FID is fully registered for messaging: https://firebase.google.com/docs/cloud-messaging/ios/get-started#access-firebase-installation-id

Please let us know if this helps, or if your client setup already matches the documentation.

[salcalderon1-tenco]

Yes I have the same problem always the notificatiosn returns FirebaseMessagingException with the error NotRegistered. My application is on flutter and update for getting the FID token and is OKAY the problem is in the backend when sent the notification by FID

[yvonnep165]

Hi @salcalderon1-tenco , thanks so much for chiming in and sharing your experience with Flutter!

Just to help us rule out the most common causes, could you double-check which Flutter package and API your client app is currently calling to generate the ID?

• If the app is calling FirebaseMessaging.instance.getToken() (from the firebase_messaging package), that generates a legacy FCM Token. If this string is passed into the backend SDK's Fid field, the backend will reject it with a NotRegistered error.
• To use the backend Fid field successfully, the client needs to generate the string using FirebaseInstallations.instance.getId() (from the firebase_app_installations package).

Additionally, building on our previous comment, could you also double-check that the FID is fully registered for messaging with the backend before the notification is sent? (You can use this guide as a quick reference for the expected registration flow: https://firebase.google.com/docs/cloud-messaging/ios/get-started#access-firebase-installation-id).

If you've verified that you are definitely using the FirebaseInstallations API and the instance is fully registered, please let us know! In that case, we'd highly recommend filing a Firebase Support Ticket with your project details. This will allow for a secure review of your project logs to figure out exactly why the FID is being rejected.