The IP address that the site gave me isn't working! It now says that there's an error. The other one worked...
Refer to the bottom of my last post, it most likely has to do with your router not having port 21 forwarded to your local computer.
The reason why it worked before is it was pointing to a private IP address on your network, so when you went to your DynDNS address it was just going to a 192.168 address, and was never going through your router. That's why it would connect.
Now that it is going to your Outside IP like it should, it's leaving your network, then coming back in, and your router isn't forwarding the port to your local computer, so it's erroring.