title: Storyboarddoesn't contain a view controller with identifier
body: <p>Hello I did some research regarding this error but unfortunately the solutions provided did not work for me. I have a project where I first started working on redViewController. Then, on the same storyboard, I added a pageviewcontroller and on the swift file added redViewController as one of its views. I changed the entry point to be the pageViewController. When I run the application the error is still looking for the redViewController. I cleaned my code and this issue still happens, do I need to update anything else? I tried using instantiateViewController(withIdentifier) but it does not find my pageViewController. Thank you for your help!</p>
  
  <p>Code:</p>
  
  <p>AppDelegate- </p>
  
  <pre><code>let storyboard = UIStoryboard(name: "Main", bundle: nil)
          //self.window?.rootViewController = storyboard.instantiateInitialViewController() //Looking for redviewController is it saved somewhere?
          self.window?.rootViewController = storyboard.instantiateViewController(withIdentifier: "PageViewController")
  self.window?.makeKeyAndVisible()
  </code></pre>