How do I troubleshoot a WordPress Site Health loopback request that returns a 401?

Yeah — a 401 means WordPress reached its own URL but got an authentication response back. That can interfere with WP-Cron and the editor's safety checks. Start by testing in Health Check troubleshooting mode: disable plugins and switch to a default theme only for your logged-in session, then turn things back on one at a time if the warning clears. Pay special attention to security/login plugins, basic-auth or password protection, and any host or CDN firewall. Also make sure the WordPress Address and Site Address use the exact public HTTPS URL. If it still happens in the stripped-down test, send your host the Site Health info and ask why a request from the origin back to the public site URL gets a 401; that usually needs an auth, firewall, or reverse-proxy rule adjusted. Don't just remove protection permanently to make the warning disappear.