Problem with sending data by ajax (laravel)

I am sending a data by ajax with type: 'post', but it generates an error, when I change it to type: 'get', the data is received in success. This is the code.

Ajax

$('.QuestionList-item').on('click', function() {
        $('.Question').show();
        $('.QuestionList').removeClass('col-12').addClass('col-6');

        var param = {
            '_token'  : $('#token').val(),
            'userid': $(this).children('.clientName').val()
        };

        $.ajax({
            url     :  "{{route('questionDetail')}}",
            type    :  'post',
            dataType:  'json',
            data    :   param,
            success :   function (data) {
                alert('send');
            },
            error   :   function() {
                alert('error');
            }
        });
    });

Blade

@foreach($questions as $question)
    <article class="QuestionList-item row middle">
        <figure class="stateIcon">
            <svg title="checkmark" viewBox="0 0 32 32" class="svgIcon detailsTitle-checkmarkSvg"><polygon points="30,5.077 26,2 11.5,22.5 4.5,15.5 1,19 12,30"></polygon></svg>
        </figure>
        <span class="ProductName">{{$question->product->name}}</span>
        <input class="clientName" type="text" value="{{$question->user_id}}">
    </article>
@endforeach

Route

Route::post('preguntas', [
'uses' => 'QuestionController@questionDetail',
'as' => 'questionDetail',
'middleware' => 'VerifyProvider']);

Driver

function questionDetail(Request $request){
    if($request->ajax()){
        $user = User::find(1);
        return response()->json([$user]);
    }
}