当我用google admob测试我的广告时，它已成功加载，但无法显示广告。日志提示为：当应用程序不在前台时，不建议显示插页式广告。
请帮助我记录日志：
17816-17816/W/Ads: It is not recommended to show an interstitial when app is not in foreground.
10:21:34.933 18115-18176/? I/c.p.r.h.LogcatAsyncReader: Heyzap: 12-07 10:21:34.682 W/c.p.a.AdsService(18115): !!!! requestAudioFocus
10:21:34.943 18115-18176/? I/c.p.r.h.LogcatAsyncReader: Heyzap: 12-07 10:21:35.069 18115-18186/? E/c.p.r.AdsApplication: [handleUncaughtException]
10:21:35.084 18115-18186/? E/c.p.r.AdsApplication: EXCEPTION: java.lang.SecurityException: Permission Denial: opening provider com.google.android.gsf.gservices.GservicesProvider from ProcessRecord{aacfdbc 18115:com.ppswipe.blurewards/u0a2} (pid=18115, uid=10002) requires com.google.android.providers.gsf.permission.READ_GSERVICES or com.google.android.providers.gsf.permission.WRITE_GSERVICES
at android.os.Parcel.readException(Parcel.java:1599)
at android.os.Parcel.readException(Parcel.java:1552)
at android.app.ActivityManagerProxy.getContentProvider(ActivityManagerNative.java:3735)
at android.app.ActivityThread.acquireProvider(ActivityThread.java:5177)
at android.app.ContextImpl$ApplicationContentResolver.acquireUnstableProvider(ContextImpl.java:2023)
at android.content.ContentResolver.acquireUnstableProvider(ContentResolver.java:1517)
at android.content.ContentResolver.query(ContentResolver.java:482)
at android.content.ContentResolver.query(ContentResolver.java:441)
at com.google.android.gms.internal.zzdnm.zza(Unknown Source)
at com.google.android.gms.internal.zzezs.zzaj(Unknown Source)
at com.google.android.gms.internal.zzezs.<init>(Unknown Source)
at com.google.android.gms.internal.zzezk.zzcmk(Unknown Source)
at com.google.android.gms.internal.zzezk.zzb(Unknown Source)
at com.google.android.gms.internal.zzezl.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
12-07 10:21:35.219 18115-18186/? E/c.p.r.AdsApplication: ---