Not getting callback in userContentController in iOS Swift?

There is a click button on my webpage, but I am not getting the click button callback from the webview in userContentController. The javascript is already implemented on the web end.

I have tried to inject the javascript from iOS end it get worked.

 override func viewDidLoad() {
        super.viewDidLoad()
        let preferences = WKPreferences()
        let contentController = WKUserContentController()
        preferences.javaScriptEnabled = true
        let source: String = """
                window.onload = function() {
                document.addEventListener("click", function(evt) {
                    var tagClicked = document.elementFromPoint(evt.clientX, evt.clientY);
                    if (window.webkit && window.webkit.messageHandlers && window.webkit.messageHandlers.getAccessToken) {
                       window.webkit.messageHandlers.Android.postMessage(JSON.stringify({
                           properties: {
                               unique_key: "some_unique_key_value"
                           }
                       }));
                    }
                });
            }
            """
        let script: WKUserScript = WKUserScript(source: source, injectionTime: .atDocumentEnd, forMainFrameOnly: true)
        contentController.addUserScript(script)
        let configuration = WKWebViewConfiguration()
        configuration.preferences = preferences
        configuration.userContentController = contentController
        configuration.userContentController.add(self, name: "Android")
        let webAppInterface = WebAppInterface(viewController: self)
        self.webView = WKWebView(frame: self.view.frame, configuration: configuration)
        webView.allowsBackForwardNavigationGestures = true
        self.webView.uiDelegate = self
        self.webView.navigationDelegate = self
        self.webView.scrollView.delegate = self
        self.view = webView
    }

But the javascript is already implemented on the web end. So, I was trying with this code.

override func viewDidLoad() {
        super.viewDidLoad()
        // Initialize WKPreferences and enable JavaScript
        let preferences = WKPreferences()
        preferences.javaScriptEnabled = true
        // Create a WKUserContentController
        let contentController = WKUserContentController()
        // Create a WKWebViewConfiguration and set its preferences and user content controller
        let configuration = WKWebViewConfiguration()
        configuration.preferences = preferences
        configuration.userContentController = contentController
        // Add the message handler to receive messages from the web end
        let webAppInterface = WebAppInterface(viewController: self)
        configuration.userContentController.add(webAppInterface, name: "Android")
        // Initialize the WKWebView with the configuration
        self.webView = WKWebView(frame: self.view.frame, configuration: configuration)
        webView.allowsBackForwardNavigationGestures = true
        self.webView.uiDelegate = self
        self.webView.navigationDelegate = self
        self.webView.scrollView.delegate = self
        self.view = webView
     }

I am getting callback whenever I am injecting the JS but I need the webend response without injecting it from my side.

 func userContentController(_ userContentController: WKUserContentController, didReceive message: WKScriptMessage) {
    
   }

I am not able to find the issue that what’s wrong I am doing in my implementation.