Boulevard Widget is not working

Custom code
1

Trying to connect self booking Boulevard widget with the following code but it is empty. Any advice?

<!-- Boulevard Self-Booking overlay -->
  <script>
    (function (a) {
      var b = {
        businessId: 'fd8c1b36-852d-42bb-bd83-19b5b000e641',
      };
  
      var c = a.createElement('script');
      var d = a.querySelector('script');
  
      c.src = 'https://static.joinboulevard.com/injector.min.js';
      c.async = true;
      c.onload = function () {
        blvd.init(b);
      };
  
      d.parentNode.insertBefore(c, d);
    })(document);
  </script>
<!-- End Boulevard Self-Booking overlay -->