Transform error, error unmarshalling XML: EOF

I am trying to transform a SOAP XML using the demo

I setup a template to transform, and set the input type as XML

[Jun 30 19:04:46] ERROR Body transform failure api_id=da76007a-6533-49ef-96d1-0022584e8092 api_name=HelloEndpointService error=error unmarshalling XML: EOF mw=TransformMiddleware org_id=1 origin= path=/HelloEndpointService/HelloEndpointService/SayHello

my template file with no variables to transform at this point:

<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:soapenv="">
      <SayHello xmlns="">

what am I doing wrong here?