I have the same problem…please find what Filezilla says,
Status: Connection established, waiting for welcome message…
Response: 220---------- Welcome to Pure-FTPd [privsep] [TLS] ----------
Response: 220-You are user number 139 of 500 allowed.
Response: 220-Local time is now 13:14. Server port: 21.
Response: 220-IPv6 connections are also welcome on this server.
Response: 220 You will be disconnected after 15 minutes of inactivity.
Command: AUTH TLS
Response: 500 This security scheme is not implemented
Command: AUTH SSL
Response: 500 This security scheme is not implemented
Error: Critical error: Could not connect to server