Unable to Press Submit Button

Question

The submit button is supposed to allow me to press it after I type something in the text field. However, It just stays greyed out. Any suggestions?

document.addEventListener("DOMContentLoaded", () => {
  document.querySelector("#submit").disabled = true;

  document.querySelector("#task").onekeyup = () => {
    if (document.querySelector("#task").value.length > 0) {
      document.querySelector("#submit").disabled = false;
    } else {
      document.querySelector("#submit").disabled = true;
    }
  };

  document.querySelector("form").onsubmit = () => {
    const task = document.querySelector("#task").value;
    const li = document.createElement("li");
    li.innerHTML = task;
    document.querySelector("#tasks").append(li);
    document.querySelector("#task").value = "";
    document.querySelector("#submit").disabled = true;
    return false;
  };
});

<h1>Tasks</h1>
<ul id="tasks"></ul>
<form>
  <input id="task" placeholder="New Task" type="text" />
  <input id="submit" type="submit" />
</form>