**Custom Server Users:**
 If your app uses a custom server for push notifications:

• Update the server's Trust Store to include the new USERTrust RSA Certification Authority certificate.
• Ensure it also retains the old certificate until the transition is complete.

Third-Party Services (e.g., Firebase, OneSignal):

• Confirm that the service provider (like Firebase) is updating their systems to include the new certificate.
• Test push notifications in the sandbox environment after January 20, 2025, to ensure everything works.

For Reference:-Apple push notification