Event listener not working with Prime

I'm using a simple JavaScript to capture button clicks for processing.  This script works fine when uploaded to SCORM Cloud but fails silently on Prime.  Any ideas?

window.cpAPIEventEmitter.addEventListener("CPAPI_INTERACTIVEITEMSUBMIT",function ( e ){

var clickedButton= e.Data.itemname;

window.cpAPIInterface.setVariableValue("clickItem",clickedButton);

});

I place this script in the actions of the master slide, then add a a few Smart Objects as buttons and a text caption to display the variable.  ON SCORM Cloud the text caption changes to the identifier of the clicked object.  In Prime it does nothing.

I dont see how to attach a sample file here but I can link one on request.