Analytics API: Interval query returns empty data for last 5 minutes

Running a custom interval report via the Analytics API for the last 5 minutes. The request is straightforward, but the response body is consistently empty, even though I know conversations are happening. I’m using the standard conversations query type. Here’s the payload:

{
 "query": {
 "filter": [
 {
 "dimension": "start_time",
 "from": "2023-10-27T14:00:00.000Z",
 "to": "2023-10-27T14:05:00.000Z"
 }
 ]
 }
}

Getting a 200 OK, just no data. Is there a latency issue or am I missing a required parameter?