I encounter this error when embedding a Threekit player:
Access to XMLHttpRequest at 'https://admin.threekit.com/api/cas/aac6c766-edd2-463a-889f-35ab1d24a55f?type=Node&bearer_token={TOKEN}' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
Check that the script tag for the Threekit player matches your org environment. If you log in to Threekit at https://admin.threekit.com make sure your script tag is <script src="https://admin.threekit.com/app/js/threekit-player.js"></script>
Make sure that your auth token is correct and authenticates the URL you are embedding on. For example, this token will load a player on localhost:3000 but not 127.0.0.1:3000