CPI Soap Error: PayLoad elements cannot fit with the message parts of the BindingOperation

I'm getting an error running a simple iflow to perform a SOAP call using a Timer, Content Modifier, and Request/Response:

java.lang.IllegalArgumentException: The PayLoad elements cannot fit with the message parts of the BindingOperation. Please check the BindingOperation and PayLoadMessage.

This error seems to be saying thay that CPI is validating the XML payload and the validation is failing before it calls the web service. I see this problem has been posted several times and several answers given and I've tried many solutions but none have corrected the problem for me.

I successfully used SOAPUI to call the same webservice method and it worked and returned a token:

When creating the iFlow I uploaded the WSDL as a resource, and in the SOAP channel I selected the LOGIN operation and SAP auto-populated the channel operation and added the namespace to the Runtime Configuration:

The SOAP connection:

I traced the payload sent to the webservice and it looked ok:

This is the error as it appeared in the log:

The WSDL is located here:

Can anyone see what I need to change to make this work?

Thanks in advance!!!