A "The connection to the server was lost" popup prevents login

When I connect to https://comm.myDomain.com:12345 , I get the following popup that prevents from login in :

I have to following HAProxy configuration :

	log /dev/log    local0
	log /dev/log    local1 debug
	chroot /var/lib/haproxy
	stats socket /run/haproxy/admin.sock mode 660 level admin expose-fd listeners
	stats timeout 10m
	user myUser
	group myUser

	# Default SSL material locations
	ca-base /usr/share/ca-certificates/mozilla
	crt-base /etc/ssl/certs

	log global
	mode    http
	option  httplog
	option  dontlognull
	option forwardfor except
	timeout connect 1m
	timeout client  10m
	timeout server  10m
	timeout check 5s
	errorfile 400 /etc/haproxy/errors/400.http
	errorfile 403 /etc/haproxy/errors/403.http
	errorfile 408 /etc/haproxy/errors/408.http
	errorfile 500 /etc/haproxy/errors/500.http
	errorfile 502 /etc/haproxy/errors/502.http
	errorfile 503 /etc/haproxy/errors/503.http
	errorfile 504 /etc/haproxy/errors/504.http

frontend http
	bind *:12345 ssl crt /etc/ssl/certs/wildcard.myDomain.com.pem
	acl url_comm_12345 hdr(host) -i comm.myDomain.com:12345
	use_backend comm_12345 if url_comm_12345

backend comm_12345
	mode http
	option forwardfor except
	cookie SERVER insert indirect nocache
	server comm01 maxconn 5000

Can you please help me ?