GraphQL fails: Getting Variable of required type "String!" was not provided

I have a Python class that worked well until 24/10/2024:

query = '''query IntrospectionQuery($typeName: String!) {
          __type(name: $typeName) {
            name
            fields {
              name
              description
              type {
                name
                kind
                ofType {
                    kind
                    name
                    ofType {
                        kind
                        name
                    }
                }
              }
            }
          }
        }'''

variables = {'typeName': type_name}

Since yesterday, I get “introspection error : Variable “$typeName” of required type “String!” was not provided”.
Writing the type-name hardcoded into the query works. Other api calls with variables (like list-items that gets board-ids) works.
Thank you