[tor-relays] "Your server (xxxx:443) has not managed to confirm that its ORPort is reachable."

I see this in syslog: Your server (xxxx:443) has not managed to confirm that its ORPort is reachable. Relays do not publish descriptors until their ORPort and DirPort are reachable. Please check your firewalls, ports, address, /etc/hosts file, etc. torrc: Nickname Contake ORPort 443 ExitRelay 0 SocksPort 0 ControlSocket 0 ContactInfo contakechuyennghicmt@gmail.com What happened and how to fix this?