Portal 2.0 or 3.0 does not load, or takes more than 5 seconds to load

If your importer isn't loading when you click the button and you've tested your solution locally and it works, you might be running into an issue with your CORS Referrer-Policy being set to `same-origin`. If you change this CORS Referrer-Policy to any other setting (which you can find all the options on MDN here), the iframe that Flatfile appears in should load properly. 

Additionally, X-Frame-Options set to DENY will cause this issue and Flatfile will be unable to load.