C# httprequest responding with error message { “message”: “refresh” }

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C#

I have two problems:

First, when I am trying to get data from this website it goes well within browser but when I send request using httpwebrequest in C# it responds with this message. In first attempt it may return data but if the send request again it returns this message.

{
    "message": "refresh"
}

Second, when I go to page-2 or click next to go to another page it generates numbers (in end) which is not consistent changes everytime I refresh browser. How can I get these numbers? For example: "=1559040099084" like this.

Link

[API]

URI used is the web address in the APILink above.

HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(URI);
            request.Headers.Add("IfModifiedSince", DateTime.Now.ToString());
            request.Method = "GET";
            string result = string.Empty;
            using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
            {
                Stream dataStream = response.GetResponseStream();
                StreamReader reader = new StreamReader(dataStream);
                result = reader.ReadToEnd();
                reader.Close();
                dataStream.Close();
            }
            Debug.Write(result);

What I have tried:

I have searched for similar questions but not getting related question. Secondly I have posted this question on Stackoverflow but didn't get any respond.