Gibbs (you wouldn't by any chance be called Leroy or Jethro right?

),
Obviously your error originates in the lack of configuration or default connections. Your user in DA/Plesk or what ever, as I understand it, is 'wiki'. Now that, by default, is always the connecting user.
You'd want to check your MODX configuration in core/config/config.inc.php and check up on the variables defined in $database_user, $database_password, $dbase and $database_dsn. Make sure all those variables check out.
The next I am wondering if why you're running a connection from a connector - is your MODX even installed (does the manager work, does the frontend)? That's be your first couple of steps in figuring this out.
Don't worry, we'll get this sorted.