I have created an html page, in which I am making the mashup call. I verified that the request arrived at the application server, checking the requestor manager and it is able to execute the pzIncludeMashupScripts activity. However, I noticed that the case that was indicated in the DIV was not triggered.
In your sample HTML page you have included script for PegaInternetApplicationComposer.js as well as pzIncludeMashupScripts ... these are the same thing but i am not sure where you got PegaInternetApplicationComposer.js from. Just use the one, the pzIncludeMashupScripts as that is returning the scripting needed to run the gadget and it's coming from the same system you want to run the gadget on.
At the bottom you also have an inline script block doing with a pega.web.api.doAction for a gadget that is not deferloaded. This is not correct as this should be done when gadget deferloaded = true and also using the pages document onLoad event.
Just start with what was generated from the case type:
Give these changes a try, they should get you further. If you get stuck though i will just help you out on a WebEx and get you past some of these initial issues so you can focus more on the POC content within the flow your trying to start.