I have created one SOAP Application to connect to QuickBooks Desktop via QuickBooksWebConnector. I have given my wsdl url to WebConnector. While calling 1st callback of authentication, connector shows me this error :

QBWC1012: Authentication failed due to following error message.
**Object reference not set to an instance of an object.** See QWCLog for more details. Remember to turn logging on.

Which ideally means : Object reference not set to an instance of an object.

When I am trying to execute this from SOAPUI or WebServiceExplorer, it shows correct response message as given below :

Request :

```
<soapenv:Envelope>
  <soapenv:Body>
    <q0:authenticate>
      <q0:strUserName>Admin</q0:strUserName>
      <q0:strPassword>Admin</q0:strPassword>
   </q0:authenticate>
  </soapenv:Body>
</soapenv:Envelope>

```

Response :

```
<soapenv:Envelope>
  <soapenv:Body>
    <authenticateResponse>
      <authenticateReturn xsi:type="ns1:ArrayOfString">
        <ns1:string>{57F3B9B1-86F1-4fcc-B1EE-566DE1813D20}</ns1:string>
        <ns1:string>none</ns1:string>
      </authenticateReturn>
    </authenticateResponse>
  </soapenv:Body>
</soapenv:Envelope>

```

(Taken from WebServiceExplorer)
As I have searched for this error : It may cause when connector gets something null or invalid in response causes this error.
How to solve this kind of error.

I am new to SOAP Webservice and also new with QuickBooks.

Thanks in advance.