Invalid site key or not loaded in api.js, Google reCAPTCHA Enterprise

Everytime I tried to render the reCAPTCHA manually using the render function I get the following error

Error: Invalid site key or not loaded in api.js: "6Lf....."

It works fine doing it the way shown in the docs

<head>
  <script src="https://www.google.com/recaptcha/enterprise.js?render=6L..."></script>
  <!-- Your code -->
</head>
<script>
  function onClick(e) {
    e.preventDefault();
    grecaptcha.enterprise.ready(async () => {
      const token = await grecaptcha.enterprise.execute('6L...', {action: 'LOGIN'});
    });
  }
</script>

But whenever I try:

<script src="https://www.google.com/recaptcha/enterprise.js?render=explicit&onload=onRecaptchaLoadCallback"></script>

// recaptcha.js
function onRecaptchaLoadCallback(){
 grecaptcha.enterprise.render('recaptcha', {
        sitekey: "6L...",
        badge: 'inline',
        size: "invisible",
        callback: function () {
            console.log('recaptcha callback');
            }
    })
}

// executed upon form onsubmit
function onClick(e) {
  e.preventDefault();
  grecaptcha.enterprise.ready(async () => {
    const token = await grecaptcha.enterprise.execute('KEY_ID', {action: 'LOGIN'});
    
  });
}

I get the above-stated error. I have already double-checked the keys and tried creating a new key, but it did not work. Any ideas as to why it doesn’t work when trying to render manually?