onLoadChildren never gets called in MediaBrowserServiceCompat

I have implemented MediaBrowserServiceCompat service in my application.

@Override
public BrowserRoot onGetRoot(@NonNull String s, int i, @Nullable Bundle bundle) {
    Log.e("testing","onGetRoot");
    return new BrowserRoot(MEDIA_ID_ROOT, null);
}

App is entering onGetRoot method when I open Android auto app in my phone, but the method onLoadChildren never gets called. So I am not able to load my music folders.

from onLoadChildren never gets called in MediaBrowserServiceCompat