sFTP stopped working

We have an established internal sFTP site which I've used with Opus for years however, over the last few months I have been unable to connect with Opus. I can connect with other tools.

Directory Opus Pro 12.23 Build 7655 x64
OS 10.0 (B:17763 P:2 T:1) SP 0.0

Below are my log entries trying to connect by both URL and IP.

Log Files:
Opening Connection 50.xxx.xxx.xxx:22
SSH: ssh_init: error during SSH connection setup 0
Connection closed
Opening Connection ftp.xxx.com:22
SSH: ssh_init: error during SSH connection setup 0
Connection closed

For reference:
Same URL via Win10 sFTP utility:
C:\Users\uskunie>sftp abc@ftp.xxxxx.com
abc@ftp.xxxxx.com's password:
Connected to abc@ftp.xxxxx.com.
sftp>

If you edit the FTP address book entry and, on the Display tab, turn on Log: Enable Debug, it might provide extra information.