After March 31, 2021 Apple Push Notification service support for the legacy binary protocol ended and users were required to move to the newer HTTP/2 APIs. (Apple's announcement).
However, if you use PubNub to deliver push notifications to Apple devices, your users will not be impacted. We have taken the necessary steps for our customers to keep the service continuity, so if your application uses APNs with PubNub, we will continue to support you. Our APNs service has been updated to automatically transition to use Apple's APNs HTTP/2 APIs.
NOTE: In case you experience any issues, please contact us at email@example.com for assistance.