Почему Cursor.fetchall() не получает результат?

def change_status(self):

        json_from_ozon = self.get_json()
        json_from_ozon = json.dumps(json_from_ozon, ensure_ascii=False)

        connector = DataBaseConnector(self.server, self.database)
        conn = connector.connection()

        try:
            with conn.cursor() as cursor:
                params = (self.id_client, json_from_ozon)

                cursor.execute(self.sql_change_status, params)


                result = cursor.fetchall()
                if result:
                    return result
                else:
                    logging.info('no result ')
        except Exception as e:
            logging.error(f'exception {e}')
        finally:
            conn.close()

Почему не возвращается результат с метода? sql_change_status =

"""
declare @res INT;
exec @res = spPartnerAPIChangeStatus 
    @idClient = ?, 
    @Json = ?;
select @res;
"""