Greetings, I had the same exact issue. I fixed the issue by following these steps. I found warnings for redundant/duplicate outlet connections to UITextFields of AthleteFormViewController in the Inspector Area and I deleted them as I already created my own IBOutlets for each of the textfields as per the book. By doing the above, I was able to edit an existing Athlete cell but still was not able to add/create a new Athlete cell. I did not change init?(coder: NSCoder) which Xcode suggested I changed the function body of @IBSegueAction function by returning AthleteFormViewController(coder: coder, athlete: nil) instead of AthleteFormViewController(coder: coder) @IBSegueAction func addButton(_ coder: NSCoder) -> AthleteFormViewController? {         return AthleteFormViewController(coder: coder, athlete: nil) } After making these changes, I was able to run the app successfully. Thanks for your time!