Drupal 7 drop down menu not showing on other pages I have the main menu with 4 links (home, services, portfolio, contact)

under "services" I created a sub-menu, (service1, service2, service3)

The problem is that the little arrow that drops down the sub-menu shows ONLY on the "services" page and NOT the other pages.

How to fix that? thanks.
To clarify:


Go to Structure/Menus;
Select the menu with the non-expanding menu item (ie. Main menu); 
Select the List Links tab if not already;
Click the "edit" link for the non-expanding menu item - the "Show as expanded" button is there.