Hello Apple Developer Community, I am reaching out for insights regarding an issue we're facing with Apple Push Notification Service (APNS). Despite successful implementation and functioning for other apps, we are consistently receiving a 400 TopicDisallowed error when trying to send push notifications to one specific app. Here's a detailed overview: Issue Summary: Push notifications sent from our server to a specific app result in a 400 TopicDisallowed error from APNS. This problem is unique to this app; notifications to other apps with similar configurations are successful. Successful Tests via Apple CloudKit Console: Notably, when using the Apple CloudKit Push Notification Console, push notifications to the problematic app are sent successfully, indicating the app's basic setup is configured correctly. Key Details: The topic field in the push notification request matches the app's bundle ID exactly. The app is downloaded from the App Store, and we are using the production environment on our server. Payload structure, APNS endpoint, and APNS Auth Key are consistent across all apps we manage. Device tokens for the problematic app validate successfully using the tool in the push notification console. Detailed server-side logging has not revealed significant differences between successful and unsuccessful push notification requests. Given these factors, we are struggling to identify the root cause of this specific issue. I am wondering if anyone in the community has faced a similar problem or could offer any insights. Any help or guidance would be immensely appreciated. Thank you in advance!