Auth0 SDK Not Passing code_verifier

I’m currently finishing up a project for a client of mine but am running into one issue preventing launch. I’m trying to set up SSO Login and Account Creation between Thinkific and my Webflow site using Auth0. When I login through my Webflow site and redirect to my Thinkific callback URL, I get an error message saying. Something went wrong when making the token request, error: {"error"=>"invalid_request", "error_description"=>"Parameter 'code_verifier' is required"}.

I tried following this guide to set up the code_verifier, but it was recommended to just use the Single Page App SDK which supposedly handles the sending of the code_verifier. Unfortunately this isn’t working for me at the moment with the below code. Did any of you with Auth0 experience happen to know what might be happening here? Any help would be much appreciated:

<script src="https://www.gstatic.com/firebasejs/6.2.3/firebase-app.js"></script>
<script src="https://www.gstatic.com/firebasejs/6.2.3/firebase-auth.js"></script>
<script src="https://www.gstatic.com/firebasejs/7.2.3/firebase-database.js"></script>
<script src="https://cdn.auth0.com/js/auth0-spa-js/1.13/auth0-spa-js.production.js"></script>
<script src="https://kit.fontawesome.com/1cd721ed46.js" crossorigin="anonymous"></script>

<script>
// Routes reserved for people who are logged in
var privatePages = [
  '/my-courses'
];

// Routes reserved for people who aren't logged in
var publicPages = [
  '/create-account',
  '/log-in'
];

let getStartedButton = document.querySelectorAll('.get-started-button');

// either with async/await
const auth0 = new Auth0Client({
  domain: 'podcatch.auth0.com',
  client_id: '{client id}'
});

console.log(auth0);
</script>
<script>
  let verifier;
  loginLink.addEventListener('click', login);
  
  function login () {    
    auth0.loginWithRedirect({
      redirect_uri: '{callback url}',
      client_id: '{id}',
      cacheLocation: 'localstorage'
    }).then(token => {
    //logged in. you can get the user profile like this:
    auth0.getUser().then(user => {
      console.log(user);
    });
  });
  };
</script>