UICollectionViewDelegate didSelectItemAt not called

Question

Please understand my bad English

I have been studying Swift right now.

This app is kind of Diary. and this ViewController shows the list of bookmarked diaries. first, Showing the list is working. The problem is when user select one of the list, it has to move to show detail of diary.

However, I don't know why UICollectionViewDelegate(didSelect) function isn't called. I used exactly same didSelect function code in the other viewcontroller. (it works)

Is there anything I have to check? or What am I missing?

P.S. : I already tried changing 'Change Interaction Enabled' options

class StarViewController: UIViewController {

    @IBOutlet weak var collectionView: UICollectionView!
    
    private var diaryList = [Diary]()

    override func viewDidLoad() {
        super.viewDidLoad()
        configureCollectionView()
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        self.loadStarDiaryList()
    }
    
    private func configureCollectionView(){
        self.collectionView.collectionViewLayout = UICollectionViewFlowLayout()
        self.collectionView.contentInset = UIEdgeInsets(top: 10, left: 10, bottom: 10, right: 10)
        self.collectionView.delegate = self
        self.collectionView.dataSource = self
    }
    
    private func loadStarDiaryList(){
        let userDefault = UserDefaults.standard
        guard let data = userDefault.object(forKey: "diaryList") as? [[String: Any]] else { return }
        self.diaryList = data.compactMap{
            guard let title = $0["title"] as? String else { return nil}
            guard let contents = $0["contents"] as? String else { return nil }
            guard let date = $0["date"] as? Date else { return nil }
            guard let isStar = $0["isStar"] as? Bool else { return nil}
            return Diary(title: title, contents: contents, date: date, isStar: isStar)
        }.filter({
            $0.isStar == true
        }).sorted(by: {
            $0.date.compare($1.date) == .orderedDescending
        })

        self.collectionView.reloadData()
    }
    
    private func dateToString(date: Date) -> String {
        let formatter = DateFormatter()
        formatter.dateFormat = "yy년 MM월 dd일(EEEEE)"
        formatter.locale = Locale(identifier: "ko_KR")
        return formatter.string(from: date)
    }
}

extension StarViewController : UICollectionViewDataSource {
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        
        print(self.diaryList.count)
        return self.diaryList.count
    }
    
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        guard let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "StarCell", for: indexPath) as? StarCell else { return UICollectionViewCell() }
        
        let diary = self.diaryList[indexPath.row]
        
        cell.titleLabel.text = diary.title
        cell.dateLabel.text = dateToString(date: diary.date)
        
        return cell
    }
}

extension StarViewController : UICollectionViewDelegateFlowLayout {
    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        return CGSize.init(width: UIScreen.main.bounds.width - 20, height: 80)
    }
}

extension StarViewController: UICollectionViewDelegate {
  func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    guard let viewController = self.storyboard?.instantiateViewController(identifier: "DiaryDetailViewController") as? DiaryDetailViewController else { return }
    let diary = self.diaryList[indexPath.row]
    viewController.diary = diary
    viewController.indexPath = indexPath
    self.navigationController?.pushViewController(viewController, animated: true)
  }
}