AdMob banner ad not showing

Question

I am using admob in my app, it was working fine but suddenly it stopped showing ads at all. Bellow is my codes i used:

mainActivity.xml:

Answer 1

In my case, I had the code below under the buildscript section of the project level build.gradle

Make sure maven {url "https://maven.google.com"} is under allProjects > repositories:

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