CloudKit notifications not being received on iOS device

If your device is not getting the push notification then you could explore the CloudKit Dashboard to check to see if it is being sent. I found that bugs on Apple's side limited push notifications to the latest 200 subscribers. Using the Bug Reporter, they corrected that error on their end.

But it seems like your device is receiving the notitifcation. (Keep in mind the device that caused the subscription to fire by affecting a change in a CloudKit file does not get/display a notification.) Check the settings in the Settings App allows the device to receive notitifcations.

I assume you have done this stuff:

UNUserNotificationCenter* center = [UNUserNotificationCenter currentNotificationCenter];
    [center requestAuthorizationWithOptions:(UNAuthorizationOptionAlert + UNAuthorizationOptionSound + UNAuthorizationOptionBadge)
            completionHandler:^(BOOL granted, NSError * _Nullable error) {
                if(error){
                }else if(granted){
                    dispatch_async(dispatch_get_main_queue(), ^{
                                      //added the if clause after testflight 1
                    if(![[UIApplication sharedApplication] isRegisteredForRemoteNotifications])
                        [[UIApplication sharedApplication] registerForRemoteNotifications];
                    });
                }else{
                    dispatch_async(dispatch_get_main_queue(), ^{
                         // issue and alert message   "you have NOT AUTHORIZED THIS DEVICE 
                       //                  TO RECEIVE THOSE ALERTS.  To authorize this device, tap 
                       //             Launch Settings App below, tap App Name tap Notifications, and then tap 
                        //                       Allow Notifications
                    });
                }
        }];

Thanks for the comments. Yes, I do call UNUserNotificationCenter's requestAuthorizationWithOptions (with alert and sound, but not badge), and if granted, I call registerForRemoteNotifications. The didRegisterForRemoteNotificationsWithDeviceToken is also called. The CloudKit dashboard shows that a push notification is generated. As I mentioned, even the iPhone's console logs seem to show that Springboard receives the notification ... it shows "Received remote notification request 0E01-5E4D [ waking: 0, hasAlertContent: 0, hasSound: 0 hasBadge: 0 hasContentAvailable: 1 hasMutableContent: 0 pushType: Alert]"

... but it just doesn't seem to pass it forward to the app. It says "NOT delivering non-notifying push notification 0E01-5E4D [pushType: Alert willNotifyUser: 0]"

Strangely, it works fine on the Mac app, which is pointing to the same private CloudKit database and uses the same CloudKit subscription.

Any thoughts? Could app signing have anything to do with this? I do have the CloudKit and Push Notifications capabilities enabled in the Xcode project file, but I generate manual provisioning profiles for the iOS app vs automatic provisioning for the Mac app. But the profiles are valid for "Development" when I'm testing this.

Turns out, it was an iOS13 problem, and wasn't working on the Release version either. Apparently, Apple changed the behavior so that when you setup a CKSubscription, the CKNotificationInfo's

alertBody

nil

Received remote notification request DB7E-4D9E [ waking: 0, hasAlertContent: 0, hasSound: 0 hasBadge: 0 hasContentAvailable: 1 hasMutableContent: 0 pushType: Background]
Process delivery of push notification DB7E-4D9E
Request DUET delivers content-available push notification to application

And then the app's didReceiveRemoteNotification (finally) gets called!

Good to know. Is this a silent notification?

yes, it's meant to be a silent notification.

With Catalina 10.15.3 (19D76) I stopped receiving silent notifications using the alertBody = nil. IOS works fine. Anyone else ?

Could you please explain more how can I achieve the same behavior using the FCM JSON request?