Audio Element not accepting correct code

https://learn.freecodecamp.org/responsive-web-design/applied-accessibility/improve-accessibility-of-audio-content-with-the-audio-element

This page isn’t working. It keeps giving me the error:

// running test
Make sure your audio element has a closing tag.
// tests completed

…but I have a closing tag:

<body>
  <header>
    <h1>Real Coding Ninjas</h1>
  </header>
  <main>
    <p>A sound clip of Zersiax's screen reader in action.</p>
    <audio id="zersiax" controls>
      <source src="https://s3.amazonaws.com/freecodecamp/screen-reader.mp3" type="audio/mpeg" />
    </audio>
  </main>
</body>

I did discover that if I remove the id="zersiax" code, then it works correctly.