Issues calling a extension's method

I have a user created extension (instance of IScriptedContentFragmentExtension) with a few methods: one that makes a POST when the user clicks a button on the front-end, and a couple of methods used for debugging. The POST method seems to work, but the debugging methods don't do anything. The code looks like this:

public ServiceResponse GetFromServiceException()
{
    throw new Exception("This is supposed to explode.");
}
 

and the requisite ServiceResponse

public class ServiceResponse : ApiEntity
    {
        public bool Succeeded { get; set; }
        public string ResponseBody { get; set; }
    }

No exception is thrown, at least as far as Admin->Monitoring->Exceptions is concerned. To be specific, nothing is returned from calling the method; I have vm code that does

#set($foo = $extension.Method())
#if($foo && !$foo.hasErrors())
do something with foo
#else
there is not a foo
#end

The widget itself is broken into parts loaded via $core_v2_widget.ExecuteFile(); the other piece of code that seems to be executed is called via POSTing to the .vm file that contains the call to the code (similar to above). Typing the name of the extension in the widget editor shows the correct autocomplete for all the methods available in the extension, so it knows it's there. 

(FWIW the ultimate goal here is to load some information from a private API via a GET - so I don't want to expose it via plain ol' jQuery, but instead have it load and be called by page load behind the scenes)

Any ideas why those methods aren't called?