Firebase Cloud Messaging Reports wrong

Question

I am sending cloud-messages to my app but Firebase-CF-Reports tells me that they would not be received:

But I know for sure that some devices do receive them. e.g. my own. So something is going wrong here in the reports.

I read about this problem here and here but I already have an analytics-label that I send with my cloud-message.

This is how I sent my notifications with java-admin-sdk:

Message message = Message.builder()
                .setTopic(topic)
                .setAndroidConfig(AndroidConfig.builder()
                        .setPriority(AndroidConfig.Priority.HIGH)
                        .build())
                .setApnsConfig(ApnsConfig.builder()
                        .setAps(Aps.builder()
                                .setMutableContent(true)
                                .setContentAvailable(true)
                                .build())
                        .putHeader("apns-push-type", "background")
                        .putHeader("apns-priority", "5")
                        .putHeader("apns-topic", "my.bundle.id")
                        .build())
                .putData("\"content\"", contentString)
                .putData("\"actionButtons\"", actionButtonsString)
                .setFcmOptions(FcmOptions.withAnalyticsLabel("SendToAll"))
                .build();

Also interesting is, that If I am not filtering for Platform/Channel (altough still filter only for my android app with Apps=) I get this:

But these numbers still don't make any sense. I also opened some notifications on my own device. And I can't believe that only 18 were received.

Has anyone an idea what I am doing wrong?

I use this fcm-sdk in my flutter app:

firebase_messaging: ^9.1.2

Solution

Despite I did not find this in the official documentation, I found information in this discussion in the comments to this answer here. Turns out that subscribing to a topic in FCM is not necessarily permanent. So don't subscribe users to a topic once. Instead do it on every app start, although it is

"not technically necessary. It may depend on your use case. For example, if you want a global topic where all users are a member of, you'd have to make sure that they are subscribed to it. Putting the subscribe method when the app starts guarantees this."

• -@AL.

Since I changed that, the Notifications are received by a lot more people than before. Only the open-count is still not working for me. It is always on zero.