Cannot query field "user" on type "Query".

[rainerbez]

I'm trying to use the Tutoral here: https://lighthouse-php.com/tutorial/#what-is-graphql but when I reach the point of trying the query:

{
user(id: 1) {
id
name
email
}
}

the reply is:
{
"errors": [
{
"message": "Cannot query field "user" on type "Query".",
"locations": [
{
"line": 2,
"column": 3
}
],
"extensions": {
"file": "/var/www/html/vendor/webonyx/graphql-php/src/Validator/Rules/FieldsOnCorrectType.php",
"line": 43
}
}
]
}

I am using a fresh installation of Laravel 12, with PHP 8.3.2. Database is seeded, and Laravel is working fine. I tried also using a different Rest client (rather than graphiql) but the result is the same. Is there any problem with using Lighthouse + Laravel 12?
Thanks for your help.

[rainerbez]

A full fresh deletion and re-installation worked...