Using Port 433 is a good Idea for ssh as the packets are indistinguishable from https.
If shields up tells you that the port is closed, it either means that
- The firewall on your router correctly lets the packets pass to your LAN, but they don't get picked up by the daemon on your machine.
- The firewall on your router is not configured to just drop packets to unwanted ports.
The second point is very unlikely - firewalls usually just drop unwanted packets, as a reply would mean sending just more unecessary traffic through the pipes, an attacker might gain knowledge from the reply, or the source IP may be spoofed (that could even mean somebody is using you to attack someone else..).
So assuming that 1. is true, it is possible that
- You have a personal firewall of some sort running on your box that is replying to the packets.
- Your ssh daemon does not accept the connection (maybe it is configured to only accept connections from certain devices, subnets, etc.)
If shields up tells you that the port is "stealth", it means that a firewall on the way silently drops the packets.
This either means that your router is misconfigured or that you are behind another NAT of some sort.
You could have added information about your way of connecting to the internet and your ISP on your question, that might have helped..