Since we have enabled the FTP access, the only problem we have found with connections seems to be the firewall blocking of FTP sites on the user side. 

We suggest that you use another domain to access the FTP site.

Sometimes users try to use the web browser to connect to the FTP.  That will not work.  You must use the ‘Windows Explorer’ window.  This is the same window that you would look for files on your computer.