Getting Error 401 unauthorized when connecting to SharePoint 2016 server in C#

Question

I am creating a simple console application that connect to SharePoint Server 2016. However, I receiver error 401 unauthorized when it gets to context.ExecuteQuery. I have no issues connecting to SharePoint Online. The issue is perculiar to SharePoint Onpremise. Below is my code

string siteUrl = "http://abc.mysharepoint.local/sites/mysite";
string userName = "myname@domain.com";
string pwd = "mypassword";
string domain = "domain.com";


using (ClientContext ctx = new ClientContext(siteUrl))
{
    try
    {
        ctx.AuthenticationMode = ClientAuthenticationMode.Default;
        ctx.Credentials = new System.Net.NetworkCredential(userName, pwd, domain);

        ctx.Load(ctx.Web, w => w.Title, w => w.Description);
        ctx.ExecuteQuery();
        Console.WriteLine(ctx.Web.Title);
    }
    catch (Exception ex)
    {

        Console.WriteLine($"{ex.Message} ");
    }
}

Please what could be the possible cause and how to resolve it. I have full admin right to the site and can access the site from the browser. I have the IP to the server configured on my computer host file.

I have checked the SharePoint Server and can confirm I have access and everything looks okay. I also tried with the credentials of a service account but am still getting same 401 unauthorized error though I have full admin access to the site.