question

 {
    "name": "Month Policy",
    "marketplaceId": "EBAY_IE",
    "returnsAccepted": true,
    "returnPeriod": {
        "value": 1,
        "unit": "MONTH"
    },
    "refundMethod": "MONEY_BACK",
    "returnShippingCostPayer": "SELLER"
} 

{
  "errors": [
    {
      "errorId": 20402,
      "domain": "API_ACCOUNT",
      "category": "REQUEST",
      "message": "Invalid input. Value isn't supported",
      "parameters": [
        {
          "name": "fieldName",
          "value": ""
        },
        {
          "name": "additionalInfo",
          "value": "Value isn't supported"
        }
      ]
    }
  ]
}