During setup, you are prompted if wish to enable SSH service, Check SSH settings in "sh run" under CLI and verify 'service sshd enable" is configured. There are additional security options under 'service sshd <parameter>".
If this is not a new installation, it's also possible that the CLI and GUI passwords are different since these are NOT automatically synced after the initial creation from the setup wizard. If the CLI admin password has been changed and lost, you might need to reset the CLI password using the recovery options listed in the link below.
