CXone v2 Reporting API: Real-time queue stats endpoint 400 error

Trying to pull live queue stats via POST /api/v2/analytics/queues/observations/query. Passing queueIds in the request body but hitting a 400 Bad Request. The payload looks right based on the Swagger spec.

POST /api/v2/analytics/queues/observations/query
Content-Type: application/json

{
  "queueIds": ["123456"],
  "interval": "PT1S"
}

Response body just says Invalid query parameter. The docs don’t mention any specific format quirks for the queueIds list. Am I missing a header or is the endpoint deprecated?