It's a 421 misdirected request from the server. The hosting company/admin is either using shared SSL certificates or has something misconfigured.
I dug a little further, and if they're using Cloudflare or another proxy on the server, there was an Apache update pushed a couple of days ago that is causing this error. Give it a day or so for the server to be updated with the fix.
Websites show "421 Misdirected Request" error