New route group always return 404

[kmergen]

What steps will reproduce the problem?

New route group.

What is the expected result?

Rendered view

What do you get instead?

404 not found error

Additional info

// config/common/routes.php

use App\Controller\SiteController;
use App\Backend\Controller\SiteController as BackendController;
use App\Controller\AccomodationController;
use Yiisoft\Router\Group;
use Yiisoft\Router\Route;

return [
    Group::create('/{_language}')
        ->routes(
            Route::get('/')->action([SiteController::class, 'index'])->name('home'),
            Route::get('/kontakt')->action([SiteController::class, 'contact'])->name('kontaktformular'),
            Route::get('/publikation')->action([SiteController::class, 'publication'])->name('publikation'),
            Route::get('/test1')->action([SiteController::class, 'test1'])->name('test1'),
            Route::get('/accomodation')->action([AccomodationController::class, 'index'])->name('overview'),
            Route::get('/unterkunft/{slug}')->action([AccomodationController::class, 'show'])->name('showaccomodation'),
        ),

    Group::create('/backend')
        ->routes(
            Route::get('/')->action([BackendController::class, 'index'])->name('dashboard'),
        ),


];

// backend/Controller/SiteController.php

namespace App\Backend\Controller;

use Psr\Http\Message\ResponseInterface;
use Yiisoft\Yii\View\ViewRenderer;
use Yiisoft\Db\Connection\ConnectionInterface;


final class SiteController
{
        
    public function __construct(private ViewRenderer $viewRenderer)
    {
        $this->viewRenderer = $viewRenderer
        ->withLayout('@resources/backend/views/layout/main')
                          ->withViewPath('@resources/backend/views');
    }

    public function index(): ResponseInterface
    {
        /** @var ConnectionInterface $db */
        // $rassen = $this->db->createCommand('SELECT * FROM {{%vdh_rassen}}')->queryAll();
        // $rows = (new Query($this->db))
        //     ->select(['name', 'ursprungsland'])
        //     ->from('{{%vdh_rassen}}')
        //     ->where(['ursprungsland' => 'Japan'])
        //     ->limit(10)
        //     ->all();
        return $this->viewRenderer->render('index');
    }
     
}

if i do something like this it works:

Group::create('/{kk}')
        ->routes(
            Route::get('/backend')->action([BackendController::class, 'index'])->name('dashboard'),
        ),

Q	A
Version	1.0.?
PHP version	8.1
Operating system	Windows 11