dropbox login page shows for a few seconds and then closed

[chicly]

var login = new DropboxLogin
(
clientId: "kzcgsmbxkxuyur2",
clientSecret: "6hu0cm96r18r4ct",
returnUrl: "https://localhost/authorize",
autoLogout: true,
loadUserInfo: false
)
{ Owner = this };
login.ShowDialog();

    if (login.IsSuccessfully)
    {
        MessageBox.Show(login.AccessToken.Value);
    }
    else
    {
        MessageBox.Show("Error............");
        this.Close();
    }