NGINX says "client sent no required SSL certificate while reading client request headers" how do we troubleshoot?
I don't see a configuration there that requires ssl client auth. Try adding
ssl_verify_client on ssl_verify_depth 3;ssl_client_certificate /path/to/accepted/CAs.pem;
(from http://nginx.org/en/docs/http/ngx_http_ssl_module.html#ssl_verify_client)