[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 Relays do not publish descriptors until their ORPort and DirPort are reachable.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?