Calling .ajaxForm()
is only initializing the Forms plugin, not doing the actual submission. You don't need to wrap it in an event handler because the plugin is taking care of everything automatically... capturing the click, blocking the default submit, and doing the ajax... otherwise, there's no point in using a plugin for this.
(You're needing to click twice because the first click is only initializing the plugin.)
Following the examples in the docs: http://malsup.com/jquery/form/
$(document).ready(function() {
$('.status_update_shipped').ajaxForm({
// your options
});
});
Also, don't forget to include the Forms plugin after you've included jQuery.
<script src="http://malsup.github.com/jquery.form.js"></script>