Getting <faultcode>soapenv:Server</faultcode><faultstring>unknown</faultstring>

I'm new to soapui and web services. I hope someone can help me with this.

I set up axis2, apache ant, mysql server on localhost:8080, but I had xampp previously installed with a mysql database installed on localhost:85.

When I run a webservice in SoapUI  to add a guest into the database, it gives me an error below:

      <soapenv:Fault>
         <faultcode>soapenv:Server</faultcode>
         <faultstring>unknown</faultstring>
         <detail>
            <ns:GuestManagementServiceGuestManagementException xmlns:ns="http://sample.com/reservation/guest/types">
               <GuestManagementException xsi:type="ax21:GuestManagementException" xmlns="http://sample.com/reservation/guest/types" xmlns:ax21="http://exception.reservation.sample.com/xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
                  <ax21:message xsi:nil="true"/>
               </GuestManagementException>
            </ns:GuestManagementServiceGuestManagementException>
         </detail>
      </soapenv:Fault>

Does anyone know how to fix this so running the webservice will add the guest into the guest database table?

Thanks.