When you using “laravel 5.5” downloaded project then showing this type of error, then first open terminal and got to project as below commands
step-1
$ cd project_name
step-2
$ composer update
Step-3
$ composer dump-autoload
After that your problem will be solve. If will not be solve then below commands
Step-4
$ composer require laravel/ui
After that run this commands. you project will be run successfully.
Step-5
$ php artisan serve
