Analytics API aggregation query grouping by queue and media type returns empty buckets

Docs state: “To retrieve aggregated analytics data, send a POST request to /api/v2/analytics/conversations/queries.” I’m trying to construct a query that groups by queue and media type to get a breakdown of handle time per channel. The request body looks like this:

{
 "groupBy": ["queue.id", "mediaType"],
 "aggregations": [
 {
 "type": "sum",
 "name": "handleTime",
 "statistic": "SUM"
 }
 ],
 "dateFrom": "2023-10-01T00:00:00.000Z",
 "dateTo": "2023-10-02T00:00:00.000Z"
}

The API returns a 200 OK, but the data array is empty. I’ve verified the date range contains traffic. Swapping groupBy to just queue.id works fine. Adding mediaType kills the results. Is there a known issue with multi-dimensional grouping in this endpoint? Or am I missing a required filter? The docs don’t mention any limitations on combining queue and media type dimensions.