Mailerlite click on pop up

Site URL: https://www.lisajonutrition.com/classes

I created a custom button on the page above using the below code. The idea is that my mailerlite form shows when the button is clicked. On the back end, this works fine. But when I pull up the website on any other computer or device, the button doesn't work. What am I missing from the code?

<div class="sqs-block button-block sqs-block-button">
  <div align="center">
  <a onclick="ml_webform_3970552('show')"
     class="sqs-block-button-element--large sqs-block-button-element" target="_blank">I'm ready to watch the class!</a>
  </div>
</div>

You can also use this plugin to create popup (when clicking on button, link, image or any link types)