Exception while calling token API for getting token

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ASP.NET

Azure

WebAPI

Hi All,

I am calling microsoft's token API for getting auth token.
I am using below code

HttpClient httpClient = new HttpClient();
httpClient.DefaultRequestHeaders.Clear();
var keyValues = new List<KeyValuePair<string, string>>();
keyValues.Add(new KeyValuePair<string, string>(GrantType, ClientCredentials));
keyValues.Add(new KeyValuePair<string, string>("client_id", ClientId));
keyValues.Add(new KeyValuePair<string, string>("client_secret", ClientSecret));
keyValues.Add(new KeyValuePair<string, string>("scope", Scope));

var url = TokenUrl;

var response = await httpClient.PostAsync(url, new FormUrlEncodedContent(keyValues));

I am getting following exception for this call when I deployed code on web server.

An error occurred while sending the request.</Message><Details>System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a send. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host

My clientId and secret are correct. This is working perfectly fine if I try this with Postman or even while debugging it locally.
But it is throwing exception when I deployed this code on web server.

Can anyone please guide me.

What I have tried:

I searched on google regarding this and tried following code before calling API:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls12;

and

System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;