Access denied. The Linux credentials provided cannot be used to log in to the SSH server running on [MACHINE]

When attempting to discover/undiscover/delete/provide credentials for a conversion for a Linux Server, the following error appears:

Access denied. The Linux credentials provided cannot be used to log in to the SSH server running on [MACHINE].
Please ensure that the user name and password are correct.

The above error can occur in cases where the user account specified does not have SSH access to the Linux server. 

To resolve the error, please verify that the user account does not have SSH access blocked.

SSH access to the source machine is blocked.

To check if the user has SSH access to the source machine, try connect using Putty or Telnet on port 22.