Pfsense, "openvpn Bad encapsulated packet length from peer (18516), which must be > 0" error solution
This problem causes from that you direct your IP:port (IP:443) to web server from Port Forwarding tab. Or you might be enabled Squid reverse proxy. Disable this direction then wou will able to connect vpn server.
And consider that you have accept rule for openvpn server from WAN interface.
I hope this helps!