In general, the error **"AXIS Engine error: couldn't find a target service to invoke. No service."** occurs if it cannot find the specified service name in the URL. Also, when I tried to access the SOAP web service from Virtual DataPort, I could access the WSDL of the web service without any issues.
Hence, you could do the following checks as mentioned below to debug this behavior in detail:
* Check the URL of the SOAP web services that you are trying to access is valid or not. Since the URL is case sensitive, check if the service name is in the same case(uppercase or lowercase) as the web service deployed in the Virtual DataPort.
* Also, to get more information about the error, check the vdp.log file available in the <DENODO_HOME>\logs\vdp directory.
Hope this helps!!