Microsoft.SharePoint.SoapServer.SoapServerException was thrown

Hi

I try to get listitem from Sharepoint, and I receive this message

Exception of type Microsoft.SharePoint.SoapServer.SoapServerException was thrown

This is my code. I have a reference to my Sharepoint Server and I work on my localhost on my work computer.

I have a problem with this line of code after de command try:
System.Xml.XmlNode nodeListItems = listService.GetListItems(listName, viewName, ndQuery, ndViewFields, rowLimit, ndQueryOptions);

Thanks for your help
 
[WebMethod]
            public string GetItemList(string sListName)
            {
                  string sReturn="";
                  
                  WindowsPrincipal p =(WindowsPrincipal)HttpContext.Current.User;
                  
                  WindowsIdentity id = (WindowsIdentity)p.Identity;

                  //Response.Output.Write("<h2>Process running as {0}</h2>",
                  //WindowsIdentity.GetCurrent().Name);

                  // impersonate temporarily
                  WindowsImpersonationContext wic = id.Impersonate();

                  
                  // Declare and initialize a variable for the Lists Web Service.
                  SharepointList.Lists listService = new SharepointList.Lists();

                  // Set the Url property of the service for the path to a subsite.
                  listService.Url = "https://intranet.2020.net/_vti_bin/Lists.asmx";
                  
                  /* Authenticate the current user by passing their default
                  credentials to the Web Service from the system credential cache.*/
                  listService.Credentials = System.Net.CredentialCache.DefaultCredentials;
                  
                  // Instantiate an XmlDocument object
                  System.Xml.XmlDocument xmlDoc = new System.Xml.XmlDocument();

                  /* Assign values to the string parameters of the GetListItems method,
                  using GUIDs for the listName and viewName variables*/
                  string listName = "{17991794-81BB-494F-9910-CFBF1093A7CF}";
                  string viewName = "{7137FFF8-48FF-4C69-8C76-0E3BBD1EA7F9}";
                  string rowLimit = "150";
                  

                  /*Use the CreateElement method of the document object to create elements
                  for the parameters that use XML*/
                  System.Xml.XmlElement ndQuery = xmlDoc.CreateElement("Query");
                  System.Xml.XmlElement ndViewFields = xmlDoc.CreateElement("ViewFields");
                  System.Xml.XmlElement ndQueryOptions = xmlDoc.CreateElement("QueryOptions");

                  /*To specify values for the parameter elements (optional), assign CAML fragments
                  to the InnerXml property of each element*/
                  ndQuery.InnerXml = "<Where><Gt><FieldRef Name=\"ID\" />" +
                        "<Value Type=\"Counter\">3</Value></Gt></Where>";
                  ndViewFields.InnerXml = "<FieldRef Name=\"Title\" />";
                  ndQueryOptions.InnerXml = "";

                  /* Declare an XmlNode object and initialize it with the XML response from
                  the GetListItems method.*/
                  
                  try
                  {
                        System.Xml.XmlNode nodeListItems = listService.GetListItems(listName, viewName, ndQuery, ndViewFields, rowLimit, ndQueryOptions);

                        // Loop through each node in the XML response and display each item.
                        foreach (System.Xml.XmlNode listItem in nodeListItems)
                        {
                              sReturn += listItem.OuterXml;
                        }
                  }
                  catch(Exception e)
                  {
                        sReturn = e.Message;
                  }
                  finally
                  {
                        wic.Undo();
                  }
                  
                  return sReturn;

            }