Iis – Can’t get access to the IIS Server

Make sure that the site binding listens on the public IP for FTP, and not just 127.0.0.1. Try testing locally using ftp://{your_public_ip} to confirm that it's setup to listen on that IP. If it works locally but not remotely, then a firewall or proxy server in-between is blocking it.

Also, try briefly to disable the Windows firewall to confirm that it's not fighting with you. Or, better yet, enable logging and check the logs after a failed attempt. That way you don't have to disable the whole firewall.

One funny thing about the EC2 public-routed IP addresses is that they aren't associated with the instance except via 1:1 NAT. So, traffic from an instance to its own public IP is in fact sent out to the gateway and routed back to it through NAT. The firewall rules are implemented somewhere in that process if I recall.

This also means that the server doesn't need to explicitly listen on anything but the RFC1918 address it has.

You need to set a firewall rule for the instance which allows inbound HTTP and anything else you might require.