FileCOPA installed OK and I can connect to it from the same machine it is installed on, but I can't connect it from another machine.
Your firewall is blocking access. The FileCOPA FTP Server needs to be able to open at least TCP ports 20 and 21. These are the standard ports for FTP access. You need to allow these ports to pass through your firewall to be able to talk to FileCOPA.
Also see How do I configure the Windows Firewall to work correctly with the FileCOPA FTP Server?