How to create an achievement?

I’m trying to experiment the new feature Achievements (Experiment) | GitLab

I created a new simple namespace under a personal account

Trying to call like this with postman:

curl --location 'https://gitlab.com/api/graphql?private_token=my-token' \
--header 'Cookie: _cfuvid=9keBlAVAE8gFNNMBk2IIX6VAyoCpOs5vqZfJP_Rbj.s-1683011153246-0-604800000' \
--form 'operations="{\"query\": \"mutation achievementsCreate($file: Upload!) {\\n  achievementsCreate(\\n    input: {namespaceId: \\\"gid://gitlab/Group/67094254\\\", name: \\\"my-test-achievement\\\", description: \\\"You'\''re awesome\\\", avatar: $file}\\n  ) {\\n    errors\\n    achievement {\\n      id\\n      name\\n      description\\n      avatarUrl\\n    }\\n  }\\n}\\n\",\"variables\": {
        \"file\":\"0\"
    },
\"operationName\": \"achievementsCreate\"}"' \
--form 'map="{\"0\":[\"variables.file\"]}"' \
--form '0=@"/Users/artemptushkin/Desktop/fry.jpeg"'

I’m getting

{
    "data": {
        "achievementsCreate": null
    },
    "errors": [
        {
            "message": "The resource that you are attempting to access does not exist or you don't have permission to perform this action",
            "locations": [
                {
                    "line": 2,
                    "column": 3
                }
            ],
            "path": [
                "achievementsCreate"
            ]
        }
    ]
}

I’m the owner of the namespace, namespace I got from the Graphql API:

query {namespace(fullPath: \"aptushkin-test-group\") { fullPath, id }}

What am I missing?