I have encountered a similar problem. I have three apps with a very low user rate, so it's easier to compare. In all three apps, when I send a notification to APNs, over two-thirds receive a "stored" status, but only one or two notifications are delivered afterward. No message is sent after that. The total number of recipients is 89; 26 were delivered to the device, and 62 were stored. One was delivered from storage, and one was discarded. All app users are located in the same region, and mobile internet or Wi-Fi is available everywhere.

Hello! I have tested it again with a single token of known user. The token has not changed and all settings or permissions are standard as in ohter apps. I do send over google firebase and the sending statistics do show the transmission to APNs. And the apple message sending statistics ... I have to wait for 2 days. to see the current status of this last message. The user is connected WiFi or mobile internet and receives messages from other apps. So I have absolutely no clue what's happening.

After two days I can see that the message is in "Stored - Device Offline" Status. But the user was online.

Is there an ongoing process for investigating the problem? because when two thirds are not transmitted to the iphone the feature is useless.