The HTTP/2-based Apple Push Notification service (APNs) provider API lets you take advantage of great features, such as authentication with a JSON Web Token, improved error messaging, and per-notification feedback. If you still send push notifications with the legacy binary protocol, make sure to upgrade to the APNs provider API as soon as possible. APNs will no longer support the legacy binary protocol after March 31, 2021.
Use of legacy binary protocol for Push Notifications - Apple has notified developers about switching to HTTP/2 based APNs provider for sending push notifications. Starting from November 2020, all notifications should be sent over the HTTP/2 protocol. [Update: Apple has extended this deadline to March 31, 2021] 1e1e36bf2d