FirebaseInitProvider: FirebaseApp initialization unsuccessful
<p>We have followed the <a href="https://firebase.google.com/docs/android/setup">Add Firebase to your Android Project</a> but we can't see the app receiving data in the Firebase Console.<br>
And when we launch the app, the log says:</p>

<pre><code>FirebaseInitProvider: FirebaseApp initialization unsuccessful
</code></pre>

<p>What does this mean? What are we doing wrong?<br>
I can't find this error in the docs, nor here in StackOverflow.</p>