Genesys Cloud Conversation Analytics API returning 422 on ServiceNow Sync

422 Unprocessable Entity

I cannot figure out why the GET /api/v2/analytics/conversations/summarized endpoint fails when called via ServiceNow MID Server. The payload matches the docs exactly, including the groupBy array for queue.id. Standard GET requests work fine. Suspect a timezone parsing issue with the interval field in Europe/London format. Any hints on the expected ISO 8601 structure?