Possible problem with handshake when requesting from API

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C#

HTTPS

Hi, I'm making a request to an API, and I'm getting this error:

"Inner: Authentication failed because the remote party sent a TLS alert: 'HandshakeFailure.
Error: The SSL connection could not be established, see inner exception."

I am working on a Windows Server 2012 R2.

The funny thing is that I installed postman and in it I have no problem to receive the API response.

This is my C# code:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12 | SecurityProtocolType.Tls13;

try
{
    var client = new HttpClient();

    var request = new HttpRequestMessage(HttpMethod.Post, "url...");
    var collection = new List<KeyValuePair<string, string>>();
    collection.Add(new("grant_type", "password"));
    collection.Add(new("username", "..."));
    collection.Add(new("password", "."));
    var content = new FormUrlEncodedContent(collection);
    request.Content = content;
    client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));
    var response = await client.SendAsync(request);
    response.EnsureSuccessStatusCode();
}
catch (Exception ex)
{
    Console.WriteLine($"Inner: {ex.InnerException.Message}");
    Console.WriteLine($"Error: {ex.Message}");
}

I appreciate any help in advance!

What I have tried:

I tried adding this line
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12 | SecurityProtocolType.Tls13;

As I saw suggested in several forums but without success.

I also tried to upgrade the .net version, I am currently using net7.