AUTH TLS problem

[microtax]

My web host has just moved me to a new server, and FileZilla can't log in with Explicit TLS (see log below).
ftptest.net says it is happy with the server.
Any ideas?

=

Status: Resolving address of ftp.topshare.com.au
Status: Connecting to 43.250.142.19:21...
Status: Connection established, waiting for welcome message...
Response: 220---------- Welcome to Pure-FTPd [privsep] [TLS] ----------
Response: 220-You are user number 8 of 100 allowed.
Response: 220-Local time is now 15:50. Server port: 21.
Response: 220-This is a private system - No anonymous login
Response: 220-IPv6 connections are also welcome on this server.
Response: 220 You will be disconnected after 15 minutes of inactivity.
Command: AUTH TLS
Error: Connection timed out after 20 seconds of inactivity
Error: Could not connect to server
Status: Waiting to retry...
Status: Resolving address of ftp.topshare.com.au
etc

[botg]

Failure to receive a reply to the AUTH command is almost always caused by a faulty or malicious firewall. Since ftptest.net succeeds, the problematic firewall is on your end of the connection.

[microtax]

I've now discovered that it will work OK if I start a VPN, but not otherwise.
Does this make any sense?

[boco]

VPN means LAN tunnel to the server. With VPN, it's like a single LAN and no router boundaries have to be crossed). If it works like this the server itself and the server's software firewall probably are OK. And if ftptest.net is happy with the server then the server's router probably is OK, too. The problem would be with the client side's outgoing connection to the internet. If VPN works, but non-VPN fails, it looks like there's something client-side trying to sabotage encrypted FTP, in the hope that client and server will fall back to plain FTP.