The operation getOrderMetrics returns 0 for all response parameters for Amazon Selling Partner API

Question

I am trying to make an API call to get order metrics from the amazon seller central page from Postman App. I have followed all the steps in the documentation. When making a request to the api to get order metrics, I m getting the response as

URL : /sales/v1/orderMetrics?marketplaceIds=ATVPDKIKX0DER&interval=2020-03-31T00:00:00Z--2021-05-01T00:00:00Z&granularity=Week&buyerType=All&firstDayOfWeek=monday&asin=B08DFGPTSK

{
  "interval": "2020-03-30T00:00Z--2020-04-06T00:00Z",
  "unitCount": 0,
  "orderItemCount": 0,
  "orderCount": 0,
  "averageUnitPrice": {
    "amount": 0,
    "currencyCode": "USD"
  },
  "totalSales": {
    "amount": 0,
    "currencyCode": "USD"
  }
}

I have tried with with different ASINs, Intervals, Granularities and Granularity Time Zones but, all it returns is zero. Please tell me if I m missing something.