Turns out I was running 4.1.9 as a GUI and 4.2.3 as a command line. Don't know how I got there. Thanks for making me look at that.

FTPS is supported since 4.2 beta only.

I've looked through the documentation, but I can't find anything there or on the WinSCP GUI itself to allow me to select FTPS as the protocol to use.

I've got it connecting via my scripted job just fine, but I'm encountering a problem when synch begins and I want to confirm behavior via the GUI to try to track down what the problem is.

So, how do I use FTPS from the GUI? I only get FTP, SCP and SFTP. Running version 4.1.9.

Thanks