Android toolbar not showing overflow menu

I Guess you missed this

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

if your phone has a physical menu button you can't see three dots

if you want to force to show three dots do as follow:

<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">

<item
    android:id="@+id/menu"
    app:showAsAction="always"
    android:icon="@drawable/ic_action_overflow"
    android:visible="true" >
 <menu>
    <item
    android:id="@+id/action_settings"
    android:orderInCategory="100"
    android:title="@string/action_settings"
    app:showAsAction="never"
    android:visible="true" />
 </menu>
</item>