Hi Dan,
Are your sure you have inserted it correctly ? When inserting that code on a template, you need to do it this way :
Using the Forms2 JS API from Landing Pages.
While all of the below examples use embedded forms, the same APIs are available on Marketo Landing Pages as well.
Usually, you'll want to add a script that gets some reference to the form object. To do this, first add your form to the landing page, then add a new HTML block to your landing page. Then you can add a script block to the page:
<script>
MktoForms2.whenReady(function (form) {
// Put your code that uses the form object here
});
</script>
-Greg
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