below code is given in which i am  printing http responce...but it is null...an nothing is printed..what is the posssible reason???

public void Method() {

  system.debug('@@@@@@@@@@'+'in method');
  HttpRequest req = new HttpRequest();
  req.setMethod('POST');
  req.setEndpoint('https://edge-beta.krollfactualdata.com/services/mismo231/kfdlos.aspx');


  String b='<REQUEST_GROUP MISMOVersionID=\'2.3.1\'><SUBMITTING_PARTY><Name>'+
  'Jefferson Funding</Name></SUBMITTING_PARTY><RECEIVING_PARTY><Name>Factual Data'+
  '</Name></RECEIVING_PARTY><REQUEST RequestDatetime=\'2003-3-24T11:30:53\''+
  'InternalAccountIdentifier=\'0610JFFUND\' LoginAccountIdentifier=\'jeffersonuser\''+
  'LoginAccountPassword=\'j3ffus3r\'><KEY><Name>HTMLFile</Name><Value>true</Value>'+
  '</KEY><KEY><Name>TextFile</Name><Value>true</Value></KEY><KEY><Name>PDFFile'+
  '</Name><Value>true</Value></KEY><REQUEST_DATA>'+
  '<CREDIT_REQUEST MISMOVersionID='+'\'2.3.1\''+' LenderCaseIdentifier='+'\'Loan#\''+
  'LenderCaseID here\' RequestingPartyRequestedByName=\'Elend Tester\'>'+
  '<CREDIT_REQUEST_DATA CreditRequestID=\'CreditReq0001\' BorrowerID=\'Borrower\''+
  ' CreditReportRequestActionType=\'Submit\' CreditReportType=\'Merge\' '+
  'CreditRequestType=\'Individual\'><CREDIT_REPOSITORY_INCLUDED>'+
  '<EquifaxIndicator>N</EquifaxIndicator><ExperianIndicator>N</ExperianIndicator>'+
  '<TransUnionIndicator>Y</TransUnionIndicator></CREDIT_REPOSITORY_INCLUDED</CREDIT_REQUEST_DATA>'+
  '<LOAN_APPLICATION><BORROWER BorrowerID=\'Borrower\'><BirthDate>1975-02-09</BirthDate>'+
  '<FirstName>Beth</FirstName><MiddleName>A</MiddleName><LastName>Bfacommon</LastName>'+
  '<PrintPositionType>Borrower</PrintPositionType><SSN>067242712</SSN>'+
  '<UnparsedName>Beth A Bfacommon</UnparsedName><MaritalStatusType>Single</MaritalStatusType>'+
  '<RESIDENCE_StreetAddress>27 E Murray</RESIDENCE_StreetAddress><City>Fantasy Island</City>'+
  '<State>IL</State><PostalCode>60750</<PostalCode>'+
  '<BorrowerResidencyDurationYears>5</BorrowerResidencyDurationYears>'+
  '</BORROWER></LOAN_APPLICATION></CREDIT_REQUEST></REQUEST_DATA>'+
  '</REQUEST></REQUEST_GROUP>';

  req.setClientCertificateName('KFDCertification');
  req.setBody(b);
  Http http = new Http(); 
  try { 
   
   HTTPResponse res = http.send(req);      
   System.debug('RRRRRRRRRR'+res.getXmlStreamReader());
   
   System.debug('response:@@@@@@@@@@@@'+res.getBody()+'PPPPPPPPP'+res.toString()); 
   } catch(System.CalloutException e)
   { 
         system.debug('@@@@@@@@@@'+'in catch'+e.getMessage());
   }
   system.debug('@@@@@@@@@@'+'out method');  */
   
}