firebase storageにあるpdfをgoogle docs viewerで表示できない。

android端末にて、firebase storageにあるpdfをgoogle docs viewerで表示できないのですが、何か問題がありますでしょうか？

端末:Pixel 5 (Android 11)

_webViewObject.Init(
    ld: (msg) =>
    {
        Debug.Log($"CallOnLoaded[{msg}]");

        const string js = @"
            if (!(window.webkit && window.webkit.messageHandlers)) {
                window.Unity = {
                    call: function(msg) {
                        window.location = 'unity:' + msg;
                    }
                };
            }
        ";

        _webViewObject.EvaluateJS(js + @"Unity.call('ua=' + navigator.userAgent)");
    },
    enableWKWebView: true);

#if UNITY_EDITOR_OSX || UNITY_STANDALONE_OSX
    _webViewObject.bitmapRefreshCycle = 1;
#endif

var Url = $"https://drive.google.com/viewerng/viewer?embedded=true&url={encodeUrl}";
_webViewObject.LoadURL(Url);

PlayerSettings->Scripting Define SymbolsにUNITYWEBVIEW_ANDROID_USES_CLEARTEXT_TRAFFICを追加
AndroidManifest.xmlにINTERNETパーミッションとandroid:usesCleartextTraffic=trueを追加

参考:
https://stackoverflow.com/questions/68509932/how-to-embed-documents-from-firebase-storage-into-google-microsoft-document-view/68514824#68514824

Start by reproducing the failure on a Pixel 5 running Android 11 using _webViewObject.LoadURL and the Google Docs viewer URL shown in the issue. Review the PlayerSettings scripting define symbol and AndroidManifest.xml settings, then compare the result with the Firebase Storage PDF flow. Done means identifying and documenting why the PDF does not display, or confirming a working display path.