Couldn't find with 'id'の解決方法（ショッピングカート機能の実装）

現在RailsでECサイトを作成中です。
カート機能を実装したいのですが、「カートに追加」のボタンをクリックすると、以下のエラーが発生します。
LineItemが判別できないというエラーと認識しております。
application.controller.rbに
include CurrentCart
before_action :set_cart　
の記述を追加しましたが、変化はありませんでした。

また、「カートに追加」のパスにはidも渡しております。
binding.pryで検証したところ、
@line_itemの値はnilとなっておりました。
解決方法の見当がつかず、情けないですが何卒お力添えの程宜しくお願い致します。

Error message

ActiveRecord::RecordNotFound at /line_items/2
Couldn't find LineItem with 'id'=2

line_items.controller

class LineItemsController < ApplicationController
 include CurrentCart
 before_action :set_line_item, only: [:show, :edit, :update, :destroy]
 before_action :set_cart, only: [:create]


 def index
   @line_items = LineItem.all
 end

 def show
 end

 def new
   @line_item = LineItem.new
 end

 def edit
 end

  def create
   item = Item.find(params[:item_id])
   @line_item = @cart.add_item(item)

   respond_to do |format|
     if @line_item.save
       format.html { redirect_to @line_item.cart, notice: 'カゴに追加されました' }
       format.json { render :show, status: :created, location: @line_item }
     else
       format.html { render :new }
       format.json { render json: @line_item.errors, status: :unprocessable_entity }
     end
   end
 end

 def update
   respond_to do |format|
     if @line_item.update(line_item_params)
       format.html { redirect_to @line_item, notice: 'Line item was successfully updated.' }
       format.json { render :show, status: :ok, location: @line_item }
     else
       format.html { render :edit }
       format.json { render json: @line_item.errors, status: :unprocessable_entity }
     end
   end
 end


 def destroy
   @cart = Cart.find(session[:cart_id])
   @line_item.destroy
   respond_to do |format|
     format.html { redirect_to cart_path(@cart), notice: 'Line item was successfully destroyed.' }
     format.json { head :no_content }
   end
 end

 private
   def set_line_item     #it says I have a problem here
     @line_item = LineItem.find(params[:id])
   end

   def line_item_params
     params.require(:line_item).permit(:item_id)
   end
end

current_cart.rb

module CurrentCart
  private
  def set_cart
    @cart = Cart.find(session[:cart_id])
  rescue ActiveRecord::RecoedNotFound
    @cart = Cart.create
    session[:cart_id] = @cart.id
  end
end

application.controller

class ApplicationController < ActionController::Base
  protect_from_forgery with: :exception
  include CurrentCart
  before_action :set_cart

end

routes

Rails.application.routes.draw do
  resources :line_items
  resources :carts
  resources :items
  devise_for :users, controllers:{
  registrations: 'registrations'
  }
  root 'items#index'
  devise_scope :user do
    get '/users/sign_out' => 'devise/sessions#destroy'
  end
end

show.html.rb(長いため省略しています）

<div class="column is-3 is-offset-1">
      <div class="bg-white pa4 border-radius-3">
        <h4 class="title is-5 has-text-centered"><%= number_to_currency(@item.price) %></h4>
        <p class="has-text-centered mb4">出品者： <%= @item.user.name %></p>
        <%= button_to '買い物カゴに追加する',line_item_path(item_id:@item), class: 'button is-warning add-to-cart' %>
      </div>
    </div>

line_item.rb

class LineItem < ApplicationRecord
  belongs_to :item
  belongs_to :cart
end

item.rb

class Item < ApplicationRecord
  before_destroy :not_refereced_by_any_line_item
  belongs_to :user, optional: true
  has_many :line_items
  mount_uploader :image, ImageUploader

validates :title, :brand, :price, :model, presence: true
validates :description, length: {maximum:1000, too_long: "%{count} 文字以内でお願いします。"}
validates :title, length: {maximum:100, too_long: "%{count} 文字以内でお願いします。"}

  BRAND = %w{ a b c d e }
  FINISH = %w{ 1週間以内 1ヶ月以内 1年以内 それ以前  }
  CONDITION = %w{ 新品 やや傷あり 傷あり かなり傷あり }

  private
  def not_refereced_by_any_line_item
    unless line_item.empty?
      errors.add(:base, "line items present")
      throw :abort
    end
  end
end

cart.rb

class Cart < ApplicationRecord
  has_many :line_items, dependent: :destroy 

  def add_item(item)
    current_item = line_items.find_by(item_id: item.id)
      if current_item
        current_item.increment(:quantity)
      else
        current_item = line_items.build(item_id: item.id)
      end
    current_item
  end
end

Server Log

Started POST "/line_items/2?item_id=2" for ::1 at 2019-10-23 18:04:28 +0900
   (0.4ms)  SET NAMES utf8,  @@SESSION.sql_mode = CONCAT(CONCAT(@@sql_mode, ',STRICT_ALL_TABLES'), ',NO_AUTO_VALUE_ON_ZERO'),  @@SESSION.sql_auto_is_null = 0, @@SESSION.wait_timeout = 2147483
   (0.3ms)  SELECT `schema_migrations`.`version` FROM `schema_migrations` ORDER BY `schema_migrations`.`version` ASC

ActionController::RoutingError (No route matches [POST] "/line_items/2"):

actionpack (6.0.0) lib/action_dispatch/middleware/debug_exceptions.rb:36:in `call'
web-console (4.0.1) lib/web_console/middleware.rb:132:in `call_app'
web-console (4.0.1) lib/web_console/middleware.rb:28:in `block in call'
web-console (4.0.1) lib/web_console/middleware.rb:17:in `catch'
web-console (4.0.1) lib/web_console/middleware.rb:17:in `call'
actionpack (6.0.0) lib/action_dispatch/middleware/show_exceptions.rb:33:in `call'
railties (6.0.0) lib/rails/rack/logger.rb:38:in `call_app'
railties (6.0.0) lib/rails/rack/logger.rb:26:in `block in call'
activesupport (6.0.0) lib/active_support/tagged_logging.rb:80:in `block in tagged'
activesupport (6.0.0) lib/active_support/tagged_logging.rb:28:in `tagged'
activesupport (6.0.0) lib/active_support/tagged_logging.rb:80:in `tagged'
railties (6.0.0) lib/rails/rack/logger.rb:26:in `call'
sprockets-rails (3.2.1) lib/sprockets/rails/quiet_assets.rb:13:in `call'
actionpack (6.0.0) lib/action_dispatch/middleware/remote_ip.rb:81:in `call'
actionpack (6.0.0) lib/action_dispatch/middleware/request_id.rb:27:in `call'
rack (2.0.7) lib/rack/method_override.rb:22:in `call'
rack (2.0.7) lib/rack/runtime.rb:22:in `call'
activesupport (6.0.0) lib/active_support/cache/strategy/local_cache_middleware.rb:29:in `call'
actionpack (6.0.0) lib/action_dispatch/middleware/executor.rb:14:in `call'
actionpack (6.0.0) lib/action_dispatch/middleware/static.rb:126:in `call'
rack (2.0.7) lib/rack/sendfile.rb:111:in `call'
actionpack (6.0.0) lib/action_dispatch/middleware/host_authorization.rb:83:in `call'
webpacker (4.0.7) lib/webpacker/dev_server_proxy.rb:29:in `perform_request'
rack-proxy (0.6.5) lib/rack/proxy.rb:57:in `call'
railties (6.0.0) lib/rails/engine.rb:526:in `call'
puma (3.12.1) lib/puma/configuration.rb:227:in `call'
puma (3.12.1) lib/puma/server.rb:660:in `handle_request'
puma (3.12.1) lib/puma/server.rb:474:in `process_client'
puma (3.12.1) lib/puma/server.rb:334:in `block in run'
puma (3.12.1) lib/puma/thread_pool.rb:135:in `block in spawn_thread'
Started GET "/line_items/2?item_id=2" for ::1 at 2019-10-23 18:04:52 +0900
Processing by LineItemsController#show as HTML
  Parameters: {"item_id"=>"2", "id"=>"2"}
  LineItem Load (0.4ms)  SELECT `line_items`.* FROM `line_items` WHERE `line_items`.`id` = 2 LIMIT 1
  ↳ app/controllers/line_items_controller.rb:61:in `set_line_item'
Completed 404 Not Found in 87ms (ActiveRecord: 3.5ms | Allocations: 20765)



ActiveRecord::RecordNotFound - Couldn't find LineItem with 'id'=2:
  app/controllers/line_items_controller.rb:61:in `set_line_item'

Started POST "/__better_errors/691901ca03d27e6b/variables" for ::1 at 2019-10-23 18:04:53 +0900
S