Custom Menu Drop down is not appearing

I have a custom menu in the sidebar which is used as the main navigation. I’m having a problem because the drop down is not appearing at all. The only way I can get it to appear is if i set a large height to the main div. My problem with doing this is that everything below the div gets pushed down. Can someone please take a look at what I’m doing wrong? If anyone could help me I’d really appreciate it. Thanks! I’ve posted this earlier but had to post again to add the link.
Website is here