If your website code contains broken external CSS or JS files, the search engine or browser crawler will receive an HTTP status code of either 4xx or 5xx. A typical illustration of this would be the 404 status code or the Not Found error, which indicates that the file in question has either been removed or relocated to a new location. It could also mean the link that leads to the file has not been modified or updated.
But you may also encounter 403 or the “Forbidden file” error. If you’re experiencing this issue, the crawler cannot access the CSS and JS files. During the web crawling, the server has most certainly stopped the crawler or requests from it.
If you have a 404 error, try restoring the JS file and then changing the link to go to the new URL by modifying the page. Make sure to verify that it’s directed to the correct folder or file, otherwise, you’ll just be starting over.