jQuery JSONP Ajax不调用

i'm trying to use yelp v2 js api.

when I try to trigger ajax call from form event, success is not fired (and nothing in firebug NET panel) I can step thru debugger to $.ajax line fine...

<script>
    $(document).ready(function() {
        $('#btnSubmit').click(function() {
            .
            .
            .

            $.ajax({
                'type': 'GET',
                'url': message.action,
                'data': parameterMap,
                'cache': true,
                'dataType': 'jsonp',
                'jsonp': false,
                'jsonpCallback': 'cb',
                'success': cbSuccess
            });
        });
    });
</script>

however, when I run same code on page load (strip out wrapper $('#btnSubmit').click(function() from above code) it works fine. why is this?