Webinar API with visual Basic n c#

We have working codes in vb.net that working in localhost.
but when the codes are published to the live IIS server. it does not work.
Do you know what we are missing?

Public Sub CallWebService(ByVal firstname As String, ByVal lastname As String,
                              ByVal email As String, ByVal id As String,
                              ByVal eventid As String, ByVal registrationid As String,
                              ByVal officephoneno As String)
            Dim client = New HttpClient()
            Dim url = "https://zoom.us/oauth/token"
            Dim requestData = New List(Of KeyValuePair(Of String, String)) From {
                New KeyValuePair(Of String, String)("grant_type", "account_credentials"),
                New KeyValuePair(Of String, String)("account_id", ""),
                New KeyValuePair(Of String, String)("client_id", ""),
                New KeyValuePair(Of String, String)("client_secret", "")
            Dim request = New HttpRequestMessage(HttpMethod.Post, url) With {
                .Content = New FormUrlEncodedContent(requestData)
            Dim response = client.SendAsync(request).Result
            Dim jsonResponse As String = response.Content.ReadAsStringAsync().Result
            Dim jsonObject As JObject = JObject.Parse(jsonResponse)
            Dim tokenValue As String = CStr(jsonObject("access_token"))
            Dim registrationData = New With
                    .first_name = firstname,
                    .last_name = lastname
            Dim jsonData As String = Newtonsoft.Json.JsonConvert.SerializeObject(registrationData)
                Using client1 As HttpClient = New HttpClient()
                    'client1.DefaultRequestHeaders.Add("Authorization", $"Bearer {tokenValue}")
                    client1.DefaultRequestHeaders.Add("Authorization", "Bearer " & tokenValue)

                    client1.DefaultRequestHeaders.Add("Accept", "application/json")
                    Dim content As HttpContent = New StringContent(jsonData, Encoding.UTF8, "application/json")
                    'Dim registrationUrl As String = $"https://api.zoom.us/v2/webinars/{id}/registrants"
                    Dim registrationUrl As String = "https://api.zoom.us/v2/webinars/" & id & "/registrants"
                    Dim response1 As HttpResponseMessage = client1.PostAsync(registrationUrl, content).Result

                    If response1.IsSuccessStatusCode Then
                        Dim responseBody As String = response1.Content.ReadAsStringAsync().Result
                        ' "Registration Successful"
                        'Return "Error: " & response1.StatusCode
                    End If
                End Using
            Catch ex As Exception
                'Return "Error"
            End Try
        Catch ex As Exception
            'Return ex.Message
        End Try
    End Sub

Hi @it13
Thanks for reaching out to us
Your request looks good to me.
Are you able to generate your access token?