Inmobi非页内广告显示带有关闭按钮的空白屏幕

Question

我正在为其中一个应用程序使用Inmobi插页式广告。广告正在加载和展示，但显示黑屏，右上角显示关闭按钮。

我使用了以下依赖项：

defaultConfig {
    applicationId "...."
    ....
    multiDexEnabled true
    ....
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:28.0.0'
implementation 'com.android.support:multidex:1.0.3'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
implementation 'com.android.support:design:28.0.0'
implementation 'com.android.support:recyclerview-v7:28.0.0'
implementation 'com.inmobi.monetization:inmobi-ads:7.2.4'
implementation 'com.google.android.gms:play-services-base:16.0.0'
implementation 'com.google.android.gms:play-services-ads:16.0.0'
implementation 'com.google.android.gms:play-services-location:16.0.0'
implementation 'com.google.android.gms:play-services-plus:16.0.0'
implementation 'com.squareup.picasso:picasso:2.5.2'

正在显示插页式广告，并调用了其所有侦听器回调。