The Crashed event filter will return sessions when your Android application crashed. Returning Crashed events for iOS requires additional configuration.
iOS differs from Android in that it selectively restricts crash and error reporting to only one endpoint. If you're sending your logs to Crashlytics, you can use our integration to also send that data to Fullstory. Otherwise, you can configure your iOS app with other common app logging frameworks.
For more information on how to configure your Android or iOS mobile application to capture error clicks, see this article: Tracking Error Clicks using Fullstory for Mobile Apps