Панель инструментов веб-отладки Symfony2 (404 не найдено)

Я устанавливаю Symfony через Composer, но когда я запускаю его из навигатора, появляется эта ошибка:

symfony web debug toolbar (404 not found)

почему он дал мне эту ошибку? Любая идея.
Спасибо

ОБНОВИТЬ

НЕ: эта ошибка появляется после запуска ccleaner!
Мой Composer.json выглядит так

{
"name": "symfony/framework-standard-edition",
"license": "MIT",
"type": "project",
"description": "The \"Symfony Standard Edition\" distribution",
"autoload": {
"psr-4": { "": "src/" }
},
"require": {
"php": ">=5.3.9",
"symfony/symfony": "2.7.*",
"doctrine/orm": "^2.4.8",
"doctrine/doctrine-bundle": "~1.4",
"symfony/assetic-bundle": "~2.3",
"symfony/swiftmailer-bundle": "~2.3",
"symfony/monolog-bundle": "~2.4",
"sensio/distribution-bundle": "~4.0",
"sensio/framework-extra-bundle": "^3.0.2",
"incenteev/composer-parameter-handler": "~2.0",
"friendsofsymfony/user-bundle": "~2.0@dev"},
"require-dev": {
"sensio/generator-bundle": "~2.3"},
"scripts": {
"post-install-cmd": [
"Incenteev\\ParameterHandler\\ScriptHandler::buildParameters",
"Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::buildBootstrap",
"Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::clearCache",
"Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installAssets",
"Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installRequirementsFile",
"Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::prepareDeploymentTarget"],
"post-update-cmd": [
"Incenteev\\ParameterHandler\\ScriptHandler::buildParameters",
"Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::buildBootstrap",
"Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::clearCache",
"Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installAssets",
"Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installRequirementsFile",
"Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::prepareDeploymentTarget"]
},
"config": {
"bin-dir": "bin"},
"extra": {
"symfony-app-dir": "app",
"symfony-web-dir": "web",
"symfony-assets-install": "relative",
"incenteev-parameters": {
"file": "app/config/parameters.yml"},
"branch-alias": {
"dev-master": "2.7-dev"}
}
}