It would be my first thought, as last time i messed with OSX it had a built in firewall that was blocking ports by default, and i had to fight to get them open. ( not for SS, but for something else i wanted to do )
The other would be checking your router.. be sure the port is manually forwarded there back to your machine. ( or have upnp enabled. ). Same here, in my case upnp was NOT enabled by default for security reasons. So i added a trigger ( instead of opening it up 24/7 )