If the Ftp2.Connect method returns a failure status (i.e. false), you can check the ConnectFailReason integer property to determine the cause of the failure:
0 = success
Normal (non-SSL) sockets:
1 = empty hostname
2 = DNS lookup failed
3 = DNS timeout
4 = Aborted by application.
5 = Internal failure.
6 = Connect Timed Out
7 = Connect Rejected (or failed for some other reason)
SSL:
100 = Internal schannel error
101 = Failed to create credentials
102 = Failed to send initial message to proxy.
103 = Handshake failed.
104 = Failed to obtain remote certificate.
Protocol/Component:
300 = asynch op in progress
301 = login failure.
