真实的广告没有在发布模式下显示,尽管proguard是不活跃的.可能是什么问题？

Question

我大约24小时前注册了admob.确认邮件来自admob.我在我的应用程序中添加了admob id.当我通过点击android studio中的运行按钮将我的应用程序安装到真实设备时,真正的广告显示正常.所以我的admob id工作正常.

但是,当我生成签名的apk并使用Android Studio终端通过apk install ...命令将apk安装到我的设备时,真实广告不会显示.我首先认为这个问题与proguard有关,但它与proguard无关.因为我停用了proguard并且真正的广告仍未显示.可能是什么问题？

build.gradle(app level):

apply plugin: 'com.android.application'
apply plugin: 'com.bugsnag.android.gradle'

android {
    compileSdkVersion 28
    buildToolsVersion '28.0.3'
    defaultConfig {
        applicationId "...."
        minSdkVersion 16
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        multiDexEnabled true
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
        debug {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.android.support:design:28.0.0'
    implementation 'com.android.support:recyclerview-v7:28.0.0'
    implementation 'jp.wasabeef:recyclerview-animators:2.2.4'
    implementation 'com.android.support:cardview-v7:28.0.0'
    implementation 'com.nex3z:flow-layout:1.1.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
    implementation 'com.google.android.gms:play-services-ads:17.1.1'
    implementation 'com.bugsnag:bugsnag-android:4.+'
}

build.gradle(项目级别)

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.2.1'
        classpath 'com.bugsnag:bugsnag-android-gradle-plugin:3.+'
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        google()
        jcenter()
        maven { url "https://maven.google.com" }
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}