Перенаправление обратно с вводом, не работающим в laravel 5.5

Я уже много раз использовал обратное перенаправление с вводом. Но в этом проекте я не могу этого сделать. Это мой метод контролер, который обрабатывает запрос формы:

public function verifyMobileCode( Request $request)
{
        $userId = Auth::user()->id;
        if ( Auth::user()->verification_code == $request['verification_code'])
        {
            User::where('id', $userId)->update(['verified'=>1]);
            return redirect('/')->with('success', 'Account verified.');
        }
        else
        {
            return redirect()->back()->withErrors('verification_code' ,'unv' )->withInput($request->all());
        }
}

Это мой клинок формы:

@extends('layouts.index')

@section('content')

<div class = "container" style='padding-top: 150px;'>

    <?php var_dump($errors) ; ?>
    <div class = "row">
        <div class = "col-md-8 col-md-offset-2">
            <div class = "panel panel-default">
                <div class = "panel-heading">Verify your mobile</div>

                <div class = "panel-body">
                    <form class = "form-horizontal" method = "POST" action = "{{ route('verifyMobileCode') }}">
                        {{ csrf_field() }}

                        <div class = "form-group{{ $errors->has('verification_code') ? ' has-error' : '' }}">
                            <label for = "verification_code" class = "col-md-4 control-label">Verification code</label>

                            <div class = "col-md-6">
                                <input id = "verification_code" type = "text" class = "form-control" name = "verification_code" value = "{!! old('verification_code') !!}" required autofocus maxlength = "6" pattern = "\d{6}">

                                @if ($errors->has('verification_code'))
                                    <span class = "help-block">
                                        <strong>Please enter 6 digit number sent to your mobile.</strong>
                                    </span>
                                @endif
                            </div>
                        </div>
                        <div class = "form-group">
                            <div class = "col-md-6 col-md-offset-4">
                                <button type = "submit" class = "btn btn-primary">
                                    Register
                                </button>
                            </div>
                        </div>
                    </form>
                </div>
            </div>
        </div>
    </div>
</div>
@endsection

Мой Kernel.php выглядит следующим образом:

<?php

namespace App\Http;

use Illuminate\Foundation\Http\Kernel as HttpKernel;

class Kernel extends HttpKernel
{
    /**
     * The application's global HTTP middleware stack.
     *
     * These middleware are run during every request to your application.
     *
     * @var array
     */
    protected $middleware = [
        \Illuminate\Foundation\Http\Middleware\CheckForMaintenanceMode::class,
        \Illuminate\Session\Middleware\StartSession::class,
        \App\Http\Middleware\LanguageSwitcher::class,
        \Illuminate\Foundation\Http\Middleware\ValidatePostSize::class,
        \App\Http\Middleware\TrimStrings::class,
        \Illuminate\Foundation\Http\Middleware\ConvertEmptyStringsToNull::class,
        \App\Http\Middleware\TrustProxies::class,
    ];

    /**
     * The application's route middleware groups.
     *
     * @var array
     */
    protected $middlewareGroups = [
        'web' => [
            \App\Http\Middleware\EncryptCookies::class,
            \Illuminate\Cookie\Middleware\AddQueuedCookiesToResponse::class,
            \Illuminate\Session\Middleware\StartSession::class,
            // \Illuminate\Session\Middleware\AuthenticateSession::class,
            \Illuminate\View\Middleware\ShareErrorsFromSession::class,
            \App\Http\Middleware\VerifyCsrfToken::class,
            \Illuminate\Routing\Middleware\SubstituteBindings::class,
        ],

        'api' => [
            'throttle:60,1',
            'bindings',
        ],
    ];

    /**
     * The application's route middleware.
     *
     * These middleware may be assigned to groups or used individually.
     *
     * @var array
     */
    protected $routeMiddleware = [
        'auth' => \Illuminate\Auth\Middleware\Authenticate::class,
        'auth.basic' => \Illuminate\Auth\Middleware\AuthenticateWithBasicAuth::class,
        'bindings' => \Illuminate\Routing\Middleware\SubstituteBindings::class,
        'can' => \Illuminate\Auth\Middleware\Authorize::class,
        'guest' => \App\Http\Middleware\RedirectIfAuthenticated::class,
        'throttle' => \Illuminate\Routing\Middleware\ThrottleRequests::class,
        'is-admin' => \App\Http\Middleware\IsAdminMiddleware::class,
    ];
}

Я не нахожу ни одной ошибки или чего-то не так. Вы что-нибудь видите? Есть ли заранее техника для отладки этого поведения? спасибо.