Newsletter Signup Mailjet

[romeo19]

Hey,
is there any way to integrate mailjet newsletter signup for a lay theme site?
currently the styling and embedding via html in the gridder, but i think the problem is in the custom javascript that is needed for the function of the newsletter signup.

this is my site: www.stage.goldenleavesfestival.de/kontakt

this is my javascript i added on the html at the top:

<script type="text/javascript" src="https://app.mailjet.com/statics/js/iframeResizer.min.js"></script>

The button for the signup is not working unfortunately. Anyone got an idea how i can fix this?

Greets and best regards.