How to implement a new invisible reCAPTCHA on a form?

I am trying to get a new "invisible" version of google reCAPTCHA working on my form.

I am using https://github.com/UndefinedOffset/silverstripe-nocaptcha

As per the docs, you should just change this value in config.yml and I assume it will be invisible?

default_size: "invisible"

      

        
        
        
      

    

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public function HelloForm() {
        $fields = new FieldList(
            new TextField('Name'),
            new EmailField('Email'),
            new TextareaField('Message')
        );
        $actions = new FieldList(
            new FormAction('doSubmitHelloForm', 'Submit')
        );

        $form = new Form($this, 'HelloForm', $fields, $actions);

        $form->enableSpamProtection()
            ->fields()->fieldByName('Captcha')
            ->setTitle("Spam protection")
            ->setDescription("Please tick the box to prove you're a human and help us stop spam.");

        return $form;
    }

      

        
        
        
      

    

config.yml

NocaptchaField:
  site_key: "MYKEYINHERE" #Your site key (required)
  secret_key: "MYKEYINHERE" #Your secret key (required)
  verify_ssl: true #Allows you to disable php-curl SSL peer verification by setting this to false (optional, defaults to true)
  default_theme: "light" #Default theme color (optional, light or dark, defaults to light)
  default_type: "image" #Default captcha type (optional, image or audio, defaults to image)
  default_size: "invisible" #Default size (optional, normal, compact or invisible, defaults to normal)
  proxy_server: "" #Your proxy server address (optional)
  proxy_auth: "" #Your proxy server authentication information (optional)

      

        
        
        
      

    

However the captcha still shows, am I missing something? (Note that I am just testing this on my local dev machine).