Webview google login not showing accounts on device

I have a progressive web app and I'm trying to create a simple app for it that has a WebView that is showing the PWA.

Everything works fine except the SSO - when the user tries to sign in, he can't see the google accounts on the device (just a standard login screen to enter email and password). If he tries to sign in from the mobile browser he can see the accounts.

Here is my code:

        webView.settings.userAgentString = System.getProperty("http.agent")
        webView.settings.javaScriptEnabled = true
        webView.settings.domStorageEnabled = true
        webView.webViewClient = WebViewClient()
        webView.webChromeClient = WebChromeClient()
        webView.loadUrl("...")