[Sendbird docs, data export overview]: The maximum data retention period for failed webhooks is six months; requesting an export older than that errors. A failed-webhook export covers at most one day (86,400,000 Unix ms from start_ts to end_ts). Check the failed webhook entry's status_code to see whether your server returned a 4xx/5xx (Sendbird retries three times and records the timestamp of the last failed attempt in time_millis), and note export links expire seven days after creation.

Context: Sendbird webhook deliveries are failing but the failed-webhook data export returns nothing or an error for old ranges.