Consuming REST API via Web application - v8

Hello Experts,

We are trying to call the REST API to get some objects from the application server. The code we have can authenticate fine against the app server (we verify this by seeing a unique session ID), however when we try to run a "simple" POST to get some entities, the app server returns HTML instead of JSON. The HTML itself contains an error message saying "Javascript is disabled". The query is the same one that swagger generates.

For this simple example, we want to retrieve all Person objects. We have a ASP.NET web application, where clicking a button calls the API to get the objects.

Private Function GetWebSession() As String
        Try
            Dim OutputSessionID As String
            Dim inputData As String
            inputData = "{""AuthString"":  ""Module=DialogUser;User=xxxxx;Password=xxxxx""}"
            Dim url As String = GetSettings.URLLogin
            Dim HttpRequest As System.Net.HttpWebRequest = CType(System.Net.HttpWebRequest.Create(url), System.Net.HttpWebRequest)
            HttpRequest.Method = "Post"

            HttpRequest.Accept = "application/json"

            HttpRequest.Timeout = 300000
            Dim inputEncoded = Encoding.ASCII.GetBytes(inputData)
            HttpRequest.GetRequestStream.Write(inputEncoded, 0, inputEncoded.Length)

            Dim cookie As New Cookie
            cookie.Domain = "xxxxxxx.xx.xx.com"
            cookie.Name = "SessionVariable"
            cookie.Value = "wsession"
            objcontainer.Add(cookie)

            HttpRequest.CookieContainer = objcontainer


            Dim HttpResponse As System.Net.HttpWebResponse = CType(HttpRequest.GetResponse(), System.Net.HttpWebResponse)

            Dim receiveStream As Stream = HttpResponse.GetResponseStream()
            Dim readStream As New StreamReader(receiveStream, Encoding.UTF8)

            Dim serializer As New System.Web.Script.Serialization.JavaScriptSerializer()
            Dim jsonobject = serializer.DeserializeObject(readStream.ReadToEnd())
            OutputSessionID = jsonobject("sessionId")

            jsonobject = Nothing
            readStream = Nothing
            receiveStream = Nothing
            HttpRequest = Nothing
            HttpResponse = Nothing

            Return OutputSessionID
        Catch ex As Exception
            Throw ex
        End Try
    End Function

Private Sub btnfilter_Click(sender As Object, e As EventArgs) Handles btnfilter.Click
        Try

            Dim url As String = "http://xxxxxxx.xxx.xxx.com:80/AppServer/api/entities/Person?loadType=Default"
            Dim HttpRequest As System.Net.HttpWebRequest = CType(System.Net.HttpWebRequest.Create(url), System.Net.HttpWebRequest)
            HttpRequest.Method = "Post"

            HttpRequest.ContentType = "application/json"
            HttpRequest.Timeout = 300000
            HttpRequest.ContentLength = 0

            HttpRequest.CookieContainer = objcontainer

)

            Dim HttpResponse As System.Net.HttpWebResponse = CType(HttpRequest.GetResponse(), System.Net.HttpWebResponse)

            Dim receiveStream As Stream = HttpResponse.GetResponseStream()
            Dim readStream As New StreamReader(receiveStream, Encoding.UTF8)

            Dim serializer As New System.Web.Script.Serialization.JavaScriptSerializer()
            Dim jsonobject = serializer.DeserializeObject(readStream.ReadToEnd())

            readStream = Nothing
            receiveStream = Nothing
            HttpRequest = Nothing
            HttpResponse = Nothing


        Catch ex As Exception
            lblnorecordsfound.Text = ex.Message
        End Try
    End Sub

Any help on why this is would be much appreciated