Navigation push is not working in custom alert

I have created my custom alert for logging out of the application but the navigation push is not working. I have also cleared the stack and assigned a new view controller to sign in

Here is my code

      try firebaseAuth.signOut()
       self.dismiss(animated: true, completion: nil)
       let domain = Bundle.main.bundleIdentifier!
       UserDefaults.standard.removePersistentDomain(forName: domain)
       UserDefaults.standard.synchronize()
       print(Array(UserDefaults.standard.dictionaryRepresentation().keys).count)
        
       let controller = storyboard?.instantiateViewController(withIdentifier: "SignInViewController") as! SignInViewController
       navigationController?.pushViewController(controller, animated: true)

       DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
         self.navigationController?.popToRootViewController(animated: true)
       }
        
        
       let signInVC = UINavigationController(rootViewController: controller)
       let appDelegate = UIApplication.shared.delegate as! AppDelegate
       appDelegate.window?.rootViewController = signInVC
        
        
     } catch let signOutError as NSError {
       self.dismiss(animated: true, completion: nil)

      print("Error signing out: %@", signOutError)
     }