About send requese get business after i'm already login

I'm C# Developer

Now I'm integrated until i'm can login and get access token already after i need to get business data to show

but i'm not sure what i'm do miss?  thanks you very much

this my error

Additional information: The remote name could not be resolved: 'api.myob.com'

this is my code

using (var client = new HttpClient())
                {
                    var url = "https://api.myob.com/au/essentials/businesses/" + obj.user.uid;
                    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
                    request.Headers.Add("Authorization", "Bearer [" + obj.access_token + "]");
                    request.Headers.Add("x-myobapi-key", "My key");
                    request.Headers.Add("x-myobapi-version", "V0");
                    request.Method = "GET";
                    request.ContentType = "application/json";

                    using (WebResponse response = request.GetResponse())
                    {

// Get data

}