Paypa Express Payment in Rails 3.2

Activemerchant.rb

#Initializer

ActiveMerchant::Billing::Base.mode = :test
    ::GATEWAY = ActiveMerchant::Billing::PaypalExpressGateway.new(
    :login => "rico_1340337222_biz_api1.gmail.com",
    :password => "I_PUT_MY_PASS_HERE",
    :signature => "I_PUT_MY_SIGNATURE_HERE",
    :allow_guest_checkout => true
  )

ERROR MESSAGE

This transaction is invalid. Please return to the recipient's website to complete your transaction using their regular checkout flow.

Return to merchant
At this time, we are unable to process your request. Please return to and try another option.

---

index.html.erb

<%= link_to image_tag('http://img36.imageshack.us/img36/249/buttonpaypal.png'), action: 'checkout', controller: 'orders'%>

order.rb

class Order < ActiveRecord::Base
	attr_accessible  :token

  def confirm
  redirect_to :action => root_path unless params[:token]
  
  details_response = ::GATEWAY.details_for(params[:token])
  
  if !details_response.success?
    @message = details_response.message
    render :action => 'error'
    return
  end
    
  @address = details_response.address
  end
  
	def new
    @order = Order.new(:express_token => params[:token])
  end

  def complete
    purchase = ::GATEWAY.purchase(5000,
      :ip       => request.remote_ip,
      :payer_id => params[:payer_id],
      :token    => params[:token]
    )
    
    if !purchase.success?
      @message = purchase.message
      render :action => 'error'
      return
    end
end
end

orders_controller.rb

class OrdersController < ApplicationController
  include ActiveMerchant::Billing 
  def checkout
  setup_response = ::GATEWAY.setup_purchase(2000,
    :ip                => request.remote_ip,
    :return_url        => url_for('confirm'),
    :cancel_return_url => url_for(root_path)
  )
  redirect_to ::GATEWAY.redirect_url_for(setup_response.token)
  end
end

route.rb

  resources :orders do
    # Im not sure why 'get :checkout' by itself doesn't work.
    get :checkout, :on => :new
    get :confirm
    get :complete
  end

 get "pages/index"