Release payment failing

I am trying to release a payment using rest api

1. I Created invoice by calling put request and was successful and get the reference Nbr
2. I called release payment object

 Payment soPaymentToBeReleased = new Payment
 {
     Type = new StringValue { Value = type },
     ReferenceNbr = new StringValue { Value = paymentRefNo }
 };

created release object

  var releasePayment = new Models.AcumaticaModels.Actions.ReleasePayment(soPaymentToBeReleased);

then I called post request

var token = await acumaticaTokenHelper.GetAccessToken();

using var httpClientPost = new HttpClient();

var requestMessage = new HttpRequestMessage(HttpMethod.Post, "https://acctqa.nabp.pharmacy/entity/NABPR2/24.200.001/Payment/ReleasePayment");

requestMessage.Headers.Add("Accept", "application/json");
requestMessage.Headers.Add("Authorization", $"Bearer {token.AccessToken}");
requestMessage.Headers.Add("PX-CbApiBranch", branch);

requestMessage.Content = new StringContent(JsonConvert.SerializeObject(soPaymentToBeReleased ), null, "application/json");

var response = await httpClientPost.SendAsync(requestMessage);

response.EnsureSuccessStatusCode();

then I receive 400 http code error with message:

The Entity field is required.

any help would be appreciated