title: rails 4 - images not showing in Heroku using Paperclip & Dropbox.
body: <p>Installed Paperclip &amp; dropbox to upload images to my application. It works in localhost but not in Heroku. It does upload an image but not from dropbox. Dropbox has been authorised with the app as well. And i get no error messages.</p>
  
  <p>dropbox.yml</p>
  
  <pre><code>app_key: "8rv2dcplixxxxxx"
  app_secret: &lt;%= ENV["APP_SECRET"] %&gt;
  access_token: "u9g1r2p59xxxxxxx"
  access_token_secret: &lt;% ENV["ACCESS_TOKEN_SECRET"] %&gt;
  user_id: "397xxxxx"
  access_type: "app_folder"
  </code></pre>
  
  <p>application.yml</p>
  
  <pre><code>APP_SECRET: "gf5tg903xxxxxxx"
  ACCESS_TOKEN_SECRET: "gpgc7xxxxxxx"
  </code></pre>
  
  <p>this is confirmed when i run heroku config </p>
  
  <p>listing.rb</p>
  
  <pre><code>class Listing &lt; ActiveRecord::Base
    if Rails.env.development?
  
      has_attached_file :image, :styles =&gt; { :medium =&gt; "200x", :thumb =&gt; "100x100&gt;" }, :default_url =&gt; "default.jpg"
      validates_attachment_content_type :image, :content_type =&gt; %w(image/jpeg image/jpg image/png)
  
    else
  
  
      has_attached_file :image, :styles =&gt; { :medium =&gt; "200x", :thumb =&gt; "100x100&gt;" }, :default_url =&gt; "default.jpg"
      validates_attachment_content_type :image, :content_type =&gt; %w(image/jpeg image/jpg image/png), 
      :storage =&gt; :dropbox,
      :dropbox_credentials =&gt; Rails.root.join("config/dropbox.yml"),
      :path =&gt; ":style/:id_:filename"
      end
  
    validates :name, :description, :price, presence: true
    validates :price, numericality: { greater_than: 0 }
    validates_attachment_presence :image
  
    belongs_to :user
    has_many :orders
  end
  </code></pre>