Did you setup a WAN rule for connections inbound to that Public IP at your ssh port?
A little more info would be helpful, not clear if you made a Wan rule or a Lan rule. Change your firewall rule and enable logging, try to connect, then see what is in the log.
Actually, are you trying to ssh to get to the command line interface or to the web based UI? Not clear on what exactly you are trying to accomplish.
I'm not personally a fan of opening up direct access to the command line or web ui on your public IP. Like I said in a previous post, I'd setup a VPN (something cert based like OpenVPN) and have it tunnel to the LAN, then you would simply connect the VPN and have access to both the web ui and the command line interface at their private/LAN IPs.