Assuming it is henrich-inc.com then it is proxied by Cloudflare so I can’t see beyond that (other than it is giving 521 as you say). Do you have access to the Cloudflare account? You could press “Pause Cloudflare on this site” and then direct access may be possible to the hosting if the host isn’t firewalled to allow only Cloudflare IPs. From there you should be able to see what the problem is. (This assumes the DNS settings in Cloudflare are correct for the hosting).