App Only Authenticated Context using client id and secret - SharePoint 2016

Hi,

 

I am trying to get App Only Authenticated Context using the below code in SharePoint 2016 but getting the following error: 

The remote server returned an error: (401) Unauthorized

 

Microsoft article says this model works for both SharePoint Online and SharePoint 2013/2016 on-premises. Is that right? 

 

string siteUrl = "https://sp2016vm:5555/sites/dev";
using (var cc = new AuthenticationManager().GetAppOnlyAuthenticatedContext(siteUrl, "[Client ID]", "[Client Secret]"))
{
    cc.Load(cc.Web, p => p.Title);
    cc.ExecuteQuery();
    Response.Write(cc.Web.Title);
};