I have found that the live activity push notification payload was changed from event -> events. https://developer.apple.com/documentation/activitykit/updating-and-ending-your-live-activity-with-activitykit-push-notifications
Is it a mistake or it has been updated?
Yes... this took a few hours of frustration. "Events" key is not working, you have to use the key "Event" but is changed in all the documentation to "Events".
Any clarification from Apple about that?
It took our team several hours of frustration.