Trello authorization is denied even with user consent

Hey everyone!

When I ask to a user to authorize my application to get his token using t.getRestApi().authorize(), I receive a authDeniedError, even when the user agree with the authorization. The popup closes before the token is stored.

This is my powerup structure:

connector.js:

"board-buttons": function (t, opts) {
      return [
        { 
          ...
          callback: (t) =>
          t
            .getRestApi()
            .isAuthorized()
            .then((isAuthorized) => {
              if (isAuthorized) {
                onBtnClick(t);
              } else
                return t.popup({
                  title: "Authorize your account",
                  url: "auth.html",
                });
            }),
          condition: "edit",
        },
      ];
    },

auth.html

<html>
  <head>
    {% load static %}
    <script src="https://p.trellocdn.com/power-up.min.js"></script>
    <link rel="stylesheet" href="https://p.trellocdn.com/power-up.min.css" />
    <style>
      select {
        height: 30px;
      }
      * {
        text-align: center;
      }
    </style>
  </head>
  <body>
    <div id="content">
      <p>We need you to authorize first!</p>
      <button id="authorize" type="submit" class="mod-primary">
        Authorize
      </button>
    </div>
  </body>
  <script src="{% static 'js/auth.js' %}"></script>
</html>
const authBtn = document.getElementById("authorize");
authBtn.addEventListener("click", () => {
  t.getRestApi()
    .authorize({ scope: "read,write" })
    .then(() => {
      t.alert({
        message: "You're authorized!",
      });
    })
    .then(() => {
      return t.closePopup();
    });
});

I’m using a django application to serve the files.