WsFederation redirects to default login page and not to MetadataAddress

Hi,

I am trying to set up a federated login scheme against AD in CMS12, .NET Core 8 using cookies, but I it redirects to the default yellow/white login screen /Util/Login?ReturnUrl=%2F both locally and on integration environment instead of redirecting to MetadataAddress. Before we ran OWIN but, now we are upgrading to latest CMS 12.

What I have done:

• I set the start page controller to [Authorize] to trigger the login
• Configuration defined in Startup.cs in ConfigureServices
• services.AddAuthentication is configurated 
  • sharedOptions.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
  • sharedOptions.DefaultSignInScheme = CookieAuthenticationDefaults.AuthenticationScheme; 
  • sharedOptions.DefaultChallengeScheme = WsFederationDefaults.AuthenticationScheme;
• AddWsFederation has defined MetadataAddress and Wtrealm (checked in debug that they are correct values) and OnSecurityTokenValidated for processing the returned security token
• AddCookie is defined with Cookie.Name, expiry and a few things to be done before login
• In Configure section I have app.UseAuthentication(); and app.UseAuthorization();

In appsettings:

    {
      "EPiServer": {
        "Login": {
          "Wtrealm": "https://our.address",
          "MetadataAddress": "https://our.address/federationmetadata/2007-06/federationmetadata.xml"
        }
      }
    }

Has anyone had this behavior before? I am thinking I missed something easy :S

/ Tony