Strange empty response from api query

Hello, I am very confused on why I am getting a weird empty response using the query metric aggregates endpoint.
 

import requests


api_key = "MY_API_KEY"
metric_id = "R3rQ9W"
page_size = 500
interval = "month"
start_date = "2022-12-30T00:00:00"
end_date = "2023-12-29T23:59:59"
measurement = "count"
by = "$message_send_cohort"


url = "https://a.klaviyo.com/api/metric-aggregates/"

payload = {
    "data": {
        "type": "metric-aggregate",
        "attributes": {
            "metric_id": metric_id,
            "interval": interval,
            "page_size": page_size,
            "timezone": "US/Eastern",
            "measurements": [measurement],
            "filter": [
                f"greater-or-equal(datetime,{start_date})",
                f"less-than(datetime,{end_date})",
            ],
            "by": [by],
        },
    }
}

headers = {
    "accept": "application/json",
    "revision": "2023-02-22",
    "content-type": "application/json",
    "Authorization": f"Klaviyo-API-Key {api_key}",
}

response = requests.post(url, json=payload, headers=headers)

response_json = response.json()
results_data = response_json["data"]

This is returning a response with no data:

{'type': 'metric-aggregate',
 'id': '-6647815704978276286',
 'attributes': {'dates': ['2022-12-01T05:00:00+00:00',
   '2023-01-01T05:00:00+00:00',
   '2023-02-01T05:00:00+00:00',
   '2023-03-01T05:00:00+00:00',
   '2023-04-01T04:00:00+00:00',
   '2023-05-01T04:00:00+00:00',
   '2023-06-01T04:00:00+00:00',
   '2023-07-01T04:00:00+00:00',
   '2023-08-01T04:00:00+00:00',
   '2023-09-01T04:00:00+00:00',
   '2023-10-01T04:00:00+00:00',
   '2023-11-01T04:00:00+00:00',
   '2023-12-01T05:00:00+00:00'],
  'data': []},
 'links': {'self': 'https://a.klaviyo.com/api/metric-aggregates/'}}

Strangely, if I change the time zone to US/Pacific, or if I change the metric, it works fine. If I change month to week instead, it works fine. Some date changes work, but not all. If I change the by to $message it works. I am a bit lost to how this could happen. It seems like somehow this is the perfect set of parameters that doesn’t work lol. Does anyone have any idea? The metric is received email.