FTP 7.5 comes with new features like Host header and SSL. I recently saw some cases coming in from our customers on this. Scanning the Internet made me realize that we need more information posted on this as far as the configuration is concerned.
If you are seeing any of these errors while connecting to an IIS FTP server using SSL/Host header like
534-Local policy on server does not allow TLS secure connections. Win32 error: Access is denied. Error details: SSL certificate was not configured.
Primary connection and data connection certificates don't match. Error: Transfer connection interrupted: ECONNABORTED - Connection aborted
431-Failed to setup secure session. Win32 error: Error details: SSL certificate hash has invalid length.
534-Protection level negotiation failed. Win32 error: Access is denied. Error details: Protection negotiation failed. PROT command with recognized parameter must precede this command.
then check this blog post here.
I wrote this article on our Team blog site hoping it reduces the confusion around this topic.