My App uses Core Data with Cloudkit when users purchased subscription (and uses only Core Data without subscription). My App should normally appear under 'Settings > [User Name] > iCloud > Apps using iCloud - Show All'; however, some users feedback that they my App cannot access iCloud (a message I displayed in my App when CKContainer.default().accountStatus is NOT available or FileManager.default.ubiquityIdentityToken == nil); and they do not see my App name under 'iCloud > Apps using iCloud - Show All'. From the screenshot that one user provided, only Apps from Apple are displayed under 'Apps using iCloud' and no third-party Apps are shown. Since the user can access to 'iCloud > Apple using iCloud', they have signed in to iCloud successfully. They have also tried to restart my App and restart the phone but the iCloud accessibility issue still remains.
How is it possible that iCloud is accessible only to Apps from Apple but not to third party Apps? What can developer do to resolve iCloud accessibility issue here?