The APNs certificate implemented in IBM Notes Traveler 9.0.1.21,will expire on 30th March and therefore the Push Notifications for Apple iOS devices will not be possible with the “default” certificate.
The easiest way to make sure that the Push Notifications functions properly is to update your Traveler Server to 10.0.0.0 or newer release. Index of all IBM Notes Traveler Releases:
http://www-01.ibm.com/support/docview.wss?uid=swg21700212#10011
In order to upgrade Traveler, there is no need to update Domino to the Version 10, although I would strongly recommend it. Traveler 10.0.X System Requirements: