At Blue Lily Studios we use WS_FTP Pro to upload files to our webservers.
We’ve used the same product for over 10 years and stand by it as a wonderful tool.

Recently we found that due to a change in webserver configuration we could no longer connect to the server using secure SSH connections.

We encountered the following error
Expected GEX Group packet from server instead of packet type 3
Failed SSH Key Exchange

To resolve this issue, open the ssh-algos.txt file which is located in 
c:\users\<username>\appdata\roaming\ipswitch\ws_ftp

In the top ===ssh-kex section, move diffie-hellman-group-exchange-sha1 to the bottom of the list of kex algos, so the new list would look like:

diffie-hellman-group1-sha1
diffie-hellman-group14-sha1
diffie-hellman-group-exchange-sha1