Getting 404 error when submitting a form

Routes:

Route::post('orders/edit-order-content/{$id}', 'Admin\OrderController@addProduct')->name('addProductToOrder');
Route::resource('/orders', 'Admin\OrderController');

Controller:

public function addProduct($id){
  dd($id);
}

View:

{!! Form::open(['route' =>['addProductToOrder',$order->id], 'id'=>'editOrderContent']) !!}
{!! Form::label('product_id','Product ID') !!}<br>
{!! Form::input('text','product_id') !!}<br>
{!! Form::label('qty','Quantity') !!}<br>
{!! Form::input('number','qty',1,['min'=>'1'])!!}<br>
{!! Form::submit('Add product',['class'=>'btn btn-info ','id'=>'addProduct']) !!}
{!! Form::close() !!}

Why am I getting 404 page? I tried to do it with new controller, but also got 404 error...

via Batmannn