插页式广告未在真实设备上展示

Question

我刚刚创建了一个新项目，我首先实现的是Interstitial ad，我将Admob像这样implementation 'com.google.android.gms:play-services-ads:17.1.3'导入到依赖项中，然后在Android Manifest中添加了我的应用程序ID

<meta-data
            android:name="com.google.android.gms.ads.APPLICATION_ID"
            android:value="My App Id"/>

现在我创建了非页内广告，我导入了我的添加单元，但它无法正常运行，它在左侧显示了这样的测试广告，如，当我构建apk并尝试将其安装在真正的设备根本不显示，所以这是我的插页式代码

   private void launchInter() {
        interstitialAd = new InterstitialAd(this);
        interstitialAd.setAdUnitId("interstitialadunit");

        //set the adListener
        interstitialAd.setAdListener(new AdListener() {
            @Override
            public void onAdLoaded() {
                showAdInter();
            }

            @Override
            public void onAdFailedToLoad(int errorCode) {
                String message = String.format("onAdFailedToLoad (%s)", getErrorReason(errorCode));
            }

            @Override
            public void onAdClosed() {
                if (exitApp)
                    finish();
            }

        });
    }

    private void showAdInter() {
        if (interstitialAd.isLoaded()) {
            interstitialAd.show();
        } else {
            Log.d("", "Intersitial ad was not ready to be shown");
        }
    }

    public void loadInterstitial() {
        AdRequest adRequest = new AdRequest.Builder()
                .addTestDevice(AdRequest.DEVICE_ID_EMULATOR)
                .addTestDevice("")
                .build();

        //Lad the interstitial aa
        interstitialAd.loadAd(adRequest);
    }

    //Get string errror reason from ad error
    private String getErrorReason(int errorCode) {
        String errorReason = "";
        switch (errorCode) {
            case AdRequest.ERROR_CODE_INTERNAL_ERROR:
                errorReason = "Internal Error";
                break;
            case AdRequest.ERROR_CODE_INVALID_REQUEST:
                errorReason = "Invalid Request";
                break;
            case AdRequest.ERROR_CODE_NETWORK_ERROR:
                errorReason = "Network Error";
                break;
            case AdRequest.ERROR_CODE_NO_FILL:
                errorReason = "No fill";
                break;
        }
        return errorReason;
    }

和onCreate方法我这样称呼

 launchInter();
    loadInterstitial();

我在做错什么，请帮忙，如果您需要更多信息，请告诉我