not popping to root view controller

whenever i press login or sign up the navigation stack is not popping to the root view controller i checked by putting log statements and it was entering the else block where it is supposed to pop to the root controller also on the login and the sign up screen there is not navigation bar as well

LoginViewController.m

• (IBAction)login:(id)sender{ NSString *username = [self.usernameField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; NSString *password = [self.passwordField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; if (([username length] == 0)||([password length] == 0)) { UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"OOPS!!" message:@"Enter valid entries" preferredStyle:UIAlertControllerStyleAlert]; UIAlertAction *defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action) {}];

  [alert addAction:defaultAction];
  [self presentViewController:alert animated:YES completion:nil];
  

  } else{ [PFUser logInWithUsernameInBackground:username password:password block:^(PFUser *user, NSError *error) { if (user) { [self.navigationController popToRootViewControllerAnimated:YES]; } else { UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"OOPS!! Something went wrong" message:[error userInfo][@"error"] preferredStyle:UIAlertControllerStyleAlert]; UIAlertAction *defaultAction = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action) {}];

                                            [alert addAction:defaultAction];
                                            [self presentViewController:alert animated:YES completion:nil];
  
                                        }}];
  

  } }