Error: FATAL ERROR: Received unexpected end-of-file from SFTP server

Symptoms

When attempting to connect to SFTP the following errors are generated:

Error: FATAL ERROR: Received unexpected end-of-file from SFTP server
Error: Could not connect to server

Description 

In this instance, this issue was caused due to the "sftp subsystem" line missing from the SSH configuration file at /etc/ssh/sshd_config.

Workaround

Adding the sftp subsystem line to the SSH configuration file at /etc/ssh/sshd_config and restarting the service should restore access to SFTP:

Subsystem sftp /usr/libexec/openssh/sftp-server

/scripts/restartsrv_sshd