Failing to Upload an Attachment from Google App Script to Zoho CRM

Failing to Upload an Attachment from Google App Script to Zoho CRM

Hi,
  I have been generally able to navigate the API without issue, but I cannot get a file that is in the form of a blob, to attach to the Account record.  I am new to programming over web APIs, so I haven't yet figured out a way to capture the corresponding HTTP POST request and response so I am flying a bit blind.  Would welcome any ideas on what is going wrong.  When I execute the code against a good recordId for an account, I receive the following response:
{code=INVALID_REQUEST, details={}, message=unable to process your request. please verify whether you have entered proper method name, parameter and parameter values., status=error}

I am working to the API described at:  https://www.zoho.com/crm/help/api/v2/#upload-an-attachment

//
// Upload a file
function uploadFile(serviceUrl, recordId , fileBlob) {
  var Service = getService();

  var requestUrl = ZOHO_URL_BASE + serviceUrl + '/' + recordId + '/Attachments';
  try {
      var response = UrlFetchApp.fetch(requestUrl, {
      headers: {
        Authorization: 'Bearer ' + Service.getAccessToken(),
      },
      method: "POST",
      'contentType': 'multipart/form-data',
      muteHttpExceptions: true,
      'payload' : fileBlob
    });
    var result = JSON.parse(response.getContentText());
    Logger.log(result);
    Logger.log(result.message);
  } catch (error) {
    Logger.log(error.toString());
  }
}

Thanks!