The push notification was rejected by APNs for some reason.
NB: Twilio push infrastructure does not support the notifications to not main certificate topic. So application device token and certificate subject must have the same bundle id. For instance, for VoIP notifications the certificate subject must end with ".voip" and the device token app bundle ends with ".voip".
Possible Causes
The push notification subject in the certificate is incorrect
The device token cannot be used with the specified subject