Is the FTP file transfer on the site down?

NO

Most Anti-virus/Internet security programs and firewalls block port 21 on your local computer by default. If you can't connect using the FTP option then you need to open port 21 in your firewall or anti-virus/internet security program.

Our end is working just fine. If you can't connect then it is your end that is blocking port 21.

Got this same message.

Disabled Windows Firewall and it worked again.

I don't recommend disabling the firewall entirely. Just go into the settings and enable port 21/FTP as an exception. Leaving the firewall open leaves your PC vulnerable.

Why not? Windows firewall is nothing but trouble.

Without the firewall all the ports of your PC are open to the internet. Even if your system is fully patched there are numerous vulnerabilities in the Windows operating system that can allow remote remote execution of code or access to your system. For example if you have printer or file sharing enabled or have a program that uses desktop SQL or the like then your system is available for attack. Even if you don't then the RDP port and the Net Logon ports and the RPC ports to name a few becomes available for outside access on your PC for people to attack which could be susceptible to a library attack to guess your password and gain access to your PC.

It is never advisable to run without a firewall. Just open the ports you need.

You don't think a router is sufficient enough?