I have been using the Google.GData.Client to retrieve some Gmail Contact data though the Google API in my web application.

See more:

C#

public static DataSet GetGmailContacts(string App_Name, string Uname, string UPassword)
        {
            DataSet ds = new DataSet();
           

              

                DataTable dt = new DataTable();
                DataColumn C2 = new DataColumn();
                C2.DataType = Type.GetType("System.String");
                C2.ColumnName = "EmailID";
                dt.Columns.Add(C2);
                try
                {

                RequestSettings rs = new RequestSettings(App_Name, Uname, UPassword);
                rs.AutoPaging = true;

                ContactsRequest cr = new ContactsRequest(rs);
                Feed<contact> f = cr.GetContacts();

                foreach (Contact t in f.Entries)
                {
                    foreach (EMail email in t.Emails)
                    {
                        DataRow dr1 = dt.NewRow();

                        dr1["EmailID"] = email.Address.ToString();

                        dt.Rows.Add(dr1);

                    }



                }

            }
            catch (Exception ex)
            {
                string str;
                str = ex.Message;
            }

                ds.Tables.Add(dt);



                return ds;
           
        }

This code was working perfectly fine until about 15 days ago and I have been using this code for the last 7 or 8 months, but now suddenly I am facing the error

Execution of authentication request returned unexpected result: 404.


When I searched google. I have searched alot but could not find any solution. Any help or guidance will be greatly appreciated.