Analytics API returning empty data for 30-min intervals

Trying to pull agent utilization metrics like tHandle and tAcw broken down by 30-minute intervals. The standard query works for daily aggregates, but when I switch the interval parameter to PT30M, the response comes back empty. No errors, just zero records. Here is the endpoint I’m hitting:

POST /api/v2/analytics/summaries/aggregates/query

Is PT30M not supported for queue summaries or do I need a different report type?