Add license check to office add-in

See more:

C#

Office

licensing

I am trying to add an license check to my office add in like described in "Add license checks to Office and SharePoint Add-ins"

public partial class Home : System.Web.UI.Page
    {
        public string etoken = "";
        private static VerificationServiceClient service = new VerificationServiceClient();
        protected void Page_Load(object sender, EventArgs e)
        {
            etoken = Request.QueryString["et"];

            if (etoken == null)
            { 
                AddInDisabled.Visible = true;
                AddInDisabled.InnerHtml = "no license";
                AddInBody.Visible = false;        
            }
            else
            {
                CallVerificationService(etoken);
                AddInDisabled.Visible = false;
                SetLanguage(Thread.CurrentThread.CurrentCulture.Name);                
            }

        }

        private void CallVerificationService(string etoken)
        {
            VerifyEntitlementTokenRequest request = new VerifyEntitlementTokenRequest();
            request.EntitlementToken = DecodeToken(etoken);
            VerifyEntitlementTokenResponse omexResponse = service.VerifyEntitlementToken(request);          
        }

        private static string DecodeToken(string encodedToken)
        {
            byte[] decodedBytes = Convert.FromBase64String(encodedToken);
            return Encoding.Unicode.GetString(decodedBytes);
        }

all values of omexRespons are equal false

What I have tried:

The toc file is in the same folder as the xml and same name I copied the example toc from "Add license checks to Office and SharePoint Add-ins" I only changed the ID and "et" = "Paid"

Am I doing something wrong? I want to check if it is a Paid license.