DhcpGetOptionValue get nothing from DHCP server?

I want to use DhcpGetOptionValue to get option from DHCP server, the result is ERROR_SUCCESS, but lpValue always repoint to NULL, Anyone could help me? thanks so much.

void CDHCPMFCDlg::OnBnClickedButton1()
{
    //search scope
    DHCP_OPTION_SCOPE_INFO scope;
 scope.ScopeType = DhcpDefaultOptions;
 scope.ScopeInfo.DefaultScopeInfo = NULL;
 scope.ScopeInfo.GlobalScopeInfo = NULL;

    //make room for returned value
    char * rpStr;
    LPDHCP_OPTION_VALUE lpValue = (LPDHCP_OPTION_VALUE)HeapAlloc(GetProcessHeap(),
        HEAP_ZERO_MEMORY,
        sizeof(DHCP_OPTION_VALUE));

    //get value of root path option for client
    DWORD readRc = DhcpGetOptionValue(L"127.0.0.1", 3, &scope, &lpValue);
    if( readRc != ERROR_SUCCESS)
    {
  AfxMessageBox(L"FAILED");
    }
    else
    {
  CString s = _T("");

  if (lpValue == NULL)// it is always TRUE
  {
   s.Format(_T("Value IS NULL."));
  }
  else
  {
   s.Format(_T("%d %d"),lpValue->OptionID,lpValue->Value.NumElements);
  }
  AfxMessageBox(s);
    }

    //free returned value, since we have a copy in rpStr
    HeapFree(GetProcessHeap(), 0, lpValue);
}

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My DHCP Server:

Option Name                       Vendor     Value                                                                                                      Class
003 Router                         Standard   10.30.0.1                                                                                                None
224 DHCP 224                    Standard   10.30.0.1;80;/Manufacturing.DataCenterAgent.XEX;/MfgBootLauncher.xex  None