WHM Transfer Tool "ssh transport failed" No RSA host key is known and you have requested strict checking. Host key verification failed.

Symptoms

Attempting to utilize Transfer Tool returns the following error:

The remote basic credential check failed due to an error 
(The password that you provided is not correct, or the SSH key is not 
permitted access: No RSA host key is known and you have 
requested strict checking. Host key verification failed.)

Description 

WHM Transfer Tool will use strict SSH Host key verification depending on the tweak setting.

WHM Server Configuration Tweak Settings

• Enable strict SSH host key checking

disabled — Do not require that the server verifies the host key of remote systems for outgoing SSH connections.

enabled — Require that the server verifies the host key of all remote systems for outgoing SSH connections. If you select enabled, you must add a host key for each remote system to the /etc/ssh/ssh_known_hosts file.

Workaround

Disable Tweak Setting "Enable strict SSH host key checking".

or

Configure the host key on the SSH ssh_known_hosts file.

Then, proceed with initiating transfer sessions once more.