SCP doesn't seem to connect (external program does)

I have been trying to get SCP sessions working via RDM, but the connection seems to hang with a "Loading......." under the / folder. Yet when I try to connect using the same credentials with winSCP it connects straight away. Is there any troubleshooting that I can do to work out why the connection is failing.

SSH connections work fine and I have even tried using linked session with the SSH connections.

Let me know if you need any screenshots/logfiles.

Andy