iOS developers get detailed subscription notifications that would let them send customers notifications if a subscription renewal fails due to a billing issue and when a billing issue has been resolved.
Detailed Subscription Notifications
Server-to-server notifications from the App Store let you receive real-time updates in a subscription’s status, so you can provide customized experiences for your subscribers. New notifications are now available when a subscription renewal fails due to a billing issue and when a billing issue is resolved by the App Store. In addition, a unified receipt containing information about the latest 100 in-app purchase transactions is now included with the notification. If you’ve already enabled server-to-server notifications in App Store Connect, you’ll automatically receive the new notifications and unified receipt for these subscription events.
Developers can learn how to enable them here.