為什么我的簡單復選框表單在提交時沒有完成其操作

const form = document.getElementById('form');
const checkbox = document.getElementById('checkbox');
const message = document.getElementById('message');

form.addEventListener('submit', function validateCheckbox(e) {
  e.preventDefault();
  if (checkbox.checked === true) {
    message.innerHTML = 'Done';
    e.currentTarget.submit();
  } else {
    message.innerHTML = 'Please check the box to continue!';
  }
})

<div class="container">
  <form method="post" action="nextPage.html" id="form">
    <label for="checkbox">By continuing, I agree that I have read and understand the terms of service.</label> <br>
    <input type="checkbox" id="checkbox">
    <button type="submit">Submit</button>
    <h5 id="message"></h5>
  </form>
</div>