Looks like Cloudflare had a problem which affected the WordOps Cloudflare IP update (there's a daily CRON job that updates an include file).
I got a bunch of these today: nginx: [emerg] host not found in set_real_ip_from "<!DOCTYPE" in /etc/nginx/conf.d/cloudflare.conf:3
The Cloudflare script that was supposed to be outputting IP addresses was outputting an error. WordOps dutifully converted that junk output into an include file which was invalid.
To fix it you can just run the script again, test and restart the stack:-
sudo /opt/cf-update.sh
sudo nginx -t
sudo wo stack reload