Have you enabled NSSupportsLiveActivitiesFrequentUpdates? Are you missing the first updates or do you get some then it pauses for awhile? (thinking your backend may not be getting the push token)

Did you enable NSSupportsLiveActivitiesFrequentUpdates? If possible I'd also try lowing the priority of the push updates on some of the states. (gate change is a 10, but flight delay is a 5) Unfortunately it feels like some of this is a bit of a black box, and the server side documentation / best practices is pretty limited.

Update: In the end, the issue ended up being the keychain not being accessible when locked. We updated to a different Keychain Accessibility Value, and that seems to have helped the main issue.

I think the input-push-token is only used for broadcast updates. We're experimenting with sending a background push notification before sending the PTS notification to "wake up" the app enough to start sending push updates. So far it is looking promising.