Neos as Headless CMS

The link i gave you is for the actual GraphQL package - the one you include is a adapter to Neos.

In the link I gave you, the installation instruction reads

And, lastly, activate the corresponding routes:

Settings.yaml:

Neos:
  Flow:
    mvc:
      routes:
        'Wwwision.GraphQL':
          variables:
            'endpoint': 'test'

and you mostlike don’t need the variables part.

At least try and see if it solves your issue. And if it does, please submit a PR to the Neos GraphQL package that explains that needed installation setup