First I tried adding the data attributes to the body element just as described i the API. I also assigned an id to the nav. I got Uncaught DOMException: Failed to execute 'querySelector' on 'Document'. I then used the Javascript initialization. I have tried straign up in a script tag and also in the like this.

 document.addEventListener("DOMContentLoaded", function(){
    const scrollSpy = new mdb.ScrollSpy(document.body, {
      target: '#main-nav'
    })
  });

Although I get no errors in the console, I dont see the active class being added.