CAGradientLayer doesn't work and still showing solid color

I'm trying to add a gradient to a view but it doesn't work. This is the code:

class TermsAndConditionViewController: UIViewController, NavigationBarToggling {
    @IBOutlet weak var tncContentView: UIView!
    @IBOutlet weak var tncTextView: UITextView!
    @IBOutlet weak var declineButton: AeonButton!
    @IBOutlet weak var acceptButton: AeonButton!
    @IBOutlet weak var unreadIndicatorView: UIView!
    @IBOutlet weak var unreadLabel: UILabel!
    
    let isNavigationBarHidden: Bool = false
    let disposeBag = DisposeBag()
    lazy var segueManager: SegueManager = {
        return SegueManager(viewController: self)
    }()
    
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        segueManager.prepare(for: segue)
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.
        setupViews()
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        title = "Terms & Conditions"
    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        
        setupGradientUnreadIndicator()
    }
    
    private func setupViews() {
        tncContentView.addCorner(radius: 8)
        tncContentView.addBorder(width: 1, color: UIColor.black.withAlphaComponent(0.1).cgColor)
    }
    
    private func setupGradientUnreadIndicator() {
        let gradient = CAGradientLayer()
        gradient.type = .axial
        gradient.colors = [
            R.color.vcSubBgColor()!.withAlphaComponent(0),
            UIColor.white
        ]
        gradient.locations = [0, 1]
        gradient.startPoint = CGPoint(x: 1, y: 0)
        gradient.startPoint = CGPoint(x: 1, y: 1)
        
        gradient.frame = unreadIndicatorView.bounds
        unreadIndicatorView.layer.insertSublayer(gradient, at: 0)
    }
}

The result is this:

As you can see, the view at the bottom of the Text View is still solid. I was expecting it will go from transparent to white. Can you help me?

Thanks.

PS: BTW, the reason I call the setupGradientUnreadIndicator() in viewDidAppear() is because my whole scene is using auto-layout. So I put it there when the frame of the view is already calculated.

As mentioned by @Larme in the comment, it is because I used UIColor instead of CGColor in the gradient.colors. After I changed it to CGColor it worked fine now.