Paysafe cards integration 3DS secure authentication pop-up doesn't appear

Feature to implement: Cards payment integration using Paysafe provider. The user shall be able to fill their card details in textFields, which are generated in an HTML file provided by Paysafe.

Implementation: There is a WebViewController that loads an HTML file with this js: https://hosted.paysafe.com/js/v1/latest/paysafe.min.js This is how it looks like: Paysafe Payment Form

Problem: After submitting the payment, a 3DS secure authentication pop-up should appear in order to enter a 4-digit code sent by SMS. Only after this verification succeeds, the payment is going through. The pop-up window in the WebViewController does not appear neither on the simulator nor on a real device.

I have tried different advice to make the pop-up window appear, but nothing is working. Here is the WebViewController:

import UIKit
import WebKit

class WebViewController: UIViewController, UIWebViewDelegate {
  
  @IBOutlet weak var webViewContainer: UIView!
  @IBOutlet weak var navItem: UINavigationItem!
  var webView: WKWebView!
  var urlToLoad = ""
  var htmlToLoad = ""
  
  let loadingIndicatorSize = CGFloat(37)
  
  var loadingIndicator: UIActivityIndicatorView
  
  private var popupWebView: WKWebView?
  
  required init?(coder aDecoder: NSCoder) {
    let loadingIndicatorFrame = CGRect(
      x: screenSize.width / 2,
      y: screenSize.height / 2 - loadingIndicatorSize * 2,
      width: loadingIndicatorSize,
      height: loadingIndicatorSize
    )
    loadingIndicator = UIActivityIndicatorView(frame: loadingIndicatorFrame) as UIActivityIndicatorView
    super.init(coder: aDecoder)
  }
  
  override func viewDidLoad() {
    super.viewDidLoad()
    navItem.leftBarButtonItem = UIBarButtonItem(title: L("Done"), style: .done, target: self, action: #selector(done))
    navItem.leftBarButtonItem?.tintColor = Colors.brand
    initWebView()
    setupNavigationItem(Colors.background)
  }
  
  override func viewDidAppear(_ animated: Bool) {
    if !urlToLoad.isEmpty {
      loadUrl()
    } else if !htmlToLoad.isEmpty {
      loadHtml()
    }
  }
  
  override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
  }
  
  @objc func done() {
    navigationController?.popViewController(animated: true)
    dismiss(animated: true, completion: nil)
  }
  
  func initWebView() {
    let webConfiguration = WKWebViewConfiguration()
    webView = WKWebView(frame: .zero, configuration: webConfiguration)
    webView.uiDelegate = self
    webView.navigationDelegate = self
    webView.allowsBackForwardNavigationGestures = true
    webView.allowsLinkPreview = true
    webView.configuration.defaultWebpagePreferences.allowsContentJavaScript = true
    webView.configuration.preferences.javaScriptCanOpenWindowsAutomatically = true
    webViewContainer.addSubview(webView)
    webViewContainer.sendSubviewToBack(webView)
    common.addConstraints(to: webView, with: webViewContainer)
  }
  
  func loadUrl() {
    if let url = URL(string: urlToLoad) {
      let request = URLRequest(url: url)
      DispatchQueue.main.async { [weak self] in
        self?.webView.load(request)
        self?.webView.allowsBackForwardNavigationGestures = true
        self?.view.setNeedsLayout()
      }
    } else {
      showAlertMessageOk(title: L("ERROR"), message: L("URL is wrong"))
    }
  }
  
  func loadHtml() {
    DispatchQueue.main.async { [weak self] in
      guard let strongSelf = self else { return }
      self?.webView.loadHTMLString(strongSelf.htmlToLoad, baseURL: nil)
      self?.webView.allowsBackForwardNavigationGestures = true
      self?.view.setNeedsLayout()
    }
  }
  
  func webView(_ webView: WKWebView, didStartProvisionalNavigation navigation: WKNavigation!) {
    startLoadingAnimation()
  }
  
  override func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
    stopLoadingAnimation()
    
//    let script = """
//                        var elements = document.getElementsByTagName("*")
//                        for (var i = 0; i < elements.length; i++) {
//                          if (elements[i].target == '_blank') {
//                            elements[i].target = '_self'
//                          }
//                        }
//                     """
//    webView.evaluateJavaScript(script, completionHandler: nil)
  }
  
  func webView(_ webView: WKWebView, didFail navigation: WKNavigation!, withError error: Error) {
    stopLoadingAnimation()
    showAlertMessageOk(title: L("Failed"), message: L("CannotLoadPage"))
  }
  
  //MARK: - Handling links containing untrusted certificates.
  func webView(_ webView: WKWebView, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
    guard let serverTrust = challenge.protectionSpace.serverTrust else {
      completionHandler(.cancelAuthenticationChallenge, nil)
      return
    }
    DispatchQueue.global(qos: .userInteractive).async {
      let exceptions = SecTrustCopyExceptions(serverTrust)
      SecTrustSetExceptions(serverTrust, exceptions)
      completionHandler(.useCredential, URLCredential(trust: serverTrust))
    }
  }
  
  func startLoadingAnimation() {
    webView.addSubview(loadingIndicator)
    loadingIndicator.hidesWhenStopped = true
    loadingIndicator.style = .medium
    loadingIndicator.startAnimating()
  }
  
  func stopLoadingAnimation() {
    loadingIndicator.stopAnimating()
    loadingIndicator.removeFromSuperview()
  }
  
  func webView(
    _ webView: WKWebView,
    createWebViewWith configuration: WKWebViewConfiguration,
    for navigationAction: WKNavigationAction,
    windowFeatures: WKWindowFeatures
  ) -> WKWebView? {
    
//    popupWebView = WKWebView(frame: view.bounds, configuration: configuration)
//    popupWebView?.autoresizingMask = [.flexibleWidth, .flexibleHeight]
//    popupWebView?.navigationDelegate = self
//    popupWebView?.uiDelegate = self
//    if let newWebview = popupWebView {
//      view.addSubview(newWebview)
//    }
//    return popupWebView ?? nil
    
    self.webView?.load(navigationAction.request)
    return nil
    
//    if navigationAction.targetFrame == nil {
//      let webViewtemp = WKWebView(
//        frame: view.bounds,
//        configuration: configuration
//      )
//      webViewtemp.navigationDelegate = self
//      webView.superview?.addSubview(webViewtemp)
//      //view.addSubview(webViewtemp)
//      //containerStack.addArrangedSubview(webViewtemp)
//      return webViewtemp
//    } else {
//      webView.load(navigationAction.request)
//      return webView
//    }
  }

  func webViewDidClose(_ webView: WKWebView) {
    webView.removeFromSuperview()
  }
  
}