Just posting this in case you run into this problem. A couple of weeks ago, I was helping a customer troubleshoot her FTP connection to the hosting company that I work for. After going through the standard troubleshooting checklist of performing trace route and telnet tests, shutting down antivirus and firewall hardware/software, and restarting the computer, I couldn’t figure out why it was connecting and then immediately terminating the connection. When I tried it on my end, it worked fine. It turns out the customer had an active VPN connection running, so once she turned it off, everything worked again. So next time you’re having trouble, try turning off your VPN.
This is the last version of FileZilla that I know of which does not auto default to using FTP over TLS when connecting to a server (i.e. it uses plain FTP to connect). Useful if you’re accustomed to and like using the Quickconnect toolbar to connect and don’t want to setup a Site profile. I made a copy and am making them available for download here in case someone (including me) needs/wants them.