WSAEPROTOTYPE error when attempting to connect via sftp

I'm having problems connecting to a remote Ubuntu 12.04.5 development system with BVRDE on Windows 10 over sftp. I was previously able to get to this system from BVRDE just fine with PAM, but when ssh is locked down with certificate authentication, I cannot get it to work. I am able to connect to this same system using PuTTY, psftp, Notepad++ and Filezilla just fine with the certificate. However, when I attempt to test a connection via BVRDE, I consistently get a messagebox with this information: "No connection Could not connect to the remote host using these parameters. System Error Message: A protocol was specified in the socket function call that does not support the semantics of the socket type requested." This appears to correspond to WSAEPROTOTYPE (10041). Running sshd -ddd while attempting to connect produces no additional messages, so the problem would appear to be on the client end. I have tried putting private.key under both the Documents/BVRDE/Solutions directory as well as the install directory containing BVRDE.exe but neither appear to work. (The Help indicates that private.key must be placed in the Project directory, which I assume refers to the Solutions directory.) I've also tried updating openssh on Ubuntu 12.04.5 to 7.1p2, but that did not change anything. Any pointers or guidance would be appreciated.

Thanks!

Mark