Cannot open connection - "Unknown Switch -explicitssl"

Executing:
open ftps://user:password@FTPServerIP/ -explicitssl -certificate="[Certificate]"

Results in:
Unknown switch 'explicitssl'

I'm running version 4.1.9. The 'implicit' switch yielded the same error. Any suggestions? Thanks.

Also, I'm able to connect fine to this FTP server using the FileZilla GUI by selecting Encryption: "Require explicit FTP over TLS". Thanks!

Please upgrade to the latest version of WinSCP.