Laravel route group issue (blank page)

config: laravel 5.5

web.php

Route::group([
    // 'middleware' => ['auth', 'is_admin'],
    'namespace'  => 'Admin',
    'prefix'     => 'admin',
    ], 
    function () {
        Route::get('/', function(){
                return 'admin';
            });

        Route::get('/pages', 'AdminController@pages')->name('admin_pages');
});

php artisan route:list http://prntscr.com/moltmg

but get http://prntscr.com/moluky empty page

I don’t know what the problem is, I’m registering the path, I’ll use group, but I’m getting a blank page, no error, nothing. Other path work fine, also if I register a path in a group, for example:
admin / dashboard
everything is fine, only this one does not work.

via Chebli Mohamed