The client needs a new connection for this request as the requested host name does not match the Server Name Indication (SNI) in use for this connection.
Before reading this, I assume you've done all the proper troubleshooting and you are 100% sure the CDN and backend server is configured correctly.
This can often happen........
haproxy is one of the best known and widely used Open Source load balancers out there and a strong competitor to nginx.
haproxy is used by many large sites per Wikipedia:
HAProxy is used by a number of high-profile websites including GoDaddy, GitHub,........