Laravel 5.5 登录和注册页面说:由于不活动，页面已过期.[TokenMismatchException]

I just created a new project of laravel version 5.5 with the laravel installer.And run the command "php artisan make:auth".The views and controller are generated for the user authentication.And also run "php artisan migrate" to create tables needed in the database.When visiting the login page and register page,filling the form and submit.It shows "The page has expired due to inactivity. Please refresh and try again.".But refreshing the page does nothing help. Seen in the source code,where causes the exception:

if ($e instanceof ModelNotFoundException) {
        $e = new NotFoundHttpException($e->getMessage(), $e);
    } elseif ($e instanceof AuthorizationException) {
        $e = new AccessDeniedHttpException($e->getMessage());
    } elseif ($e instanceof TokenMismatchException) {
        $e = new HttpException(419, $e->getMessage());
    }

似乎是TokenMismatchException"导致了这个问题.这是什么时候发生的?为什么?我只是创建了这个新项目，没有做任何其他更改.希望你得到积分.我使用 php 7.1.9(laravel 5.5 需要 php > 7.0.0).并在开发环境中使用:php artisan serve