Invalid Api credentials response code 11

Hello Everyone,
I am using REST API to fetch the data from 3rd party using POST method, I have used the same parameters in Header, Body in postman and it is giving me the data in json format, but when I am using the same thing in power query of power bi, it is giving me an error: Response Msg: Invalid APi credentials, Response code:11 & response : NULL, Please have a look in my power query below and tell me what's is wrong in this :-

let
ApiOwner= "________",
ApiKey="________",
url = "https://dentalkart.vineretail.com/RestWS/api/eretail/v3/sku/inventoryStatus",
header= [#"Authorization" = ApiKey & ApiOwner,
#"Content-Type" = "application/x-www-form-urlencoded"],

RequestBody=
"{
""skuCodes"":""[]"",
""fromDate"":""18/06/2021 15:40:30"",
""toDate"":""23/06/2021 15:40:30"",
""pageNumber"":""1"",
""dropShipFlag"":""no"",
""locCode"":""
}",

webdata = Web.Contents(url, [Content = Text.ToBinary(RequestBody), Headers=header]),
response = Json.Document(webdata)

in
response

Any kind of help would really be appreciated ! API Call Credentials Invalid