Firebase Token Authentication error : <p>I am using firebase storage to upload files , but when I upload I am getting this error</p>

<pre><code>E/StorageUtil: error getting token java.util.concurrent.ExecutionException: com.google.android.gms.internal.zzand: Please sign in before trying to get a token.
</code></pre>

<p>I googled it but couldn't get answer for it! 
I have signed in, in firebase.</p>
