Upcoming Events widget not working but 'Most Popular Events' widget works fine. Why?

I want to have a list of upcoming events in one of my side bars. Here is the link.

http://www.smartchangesolutions.com/resources/

I tried 'Upcoming Events' but nothing shows up on the sidebar. Yet when I put the 'Most Popular Events' they show up just fine. This works fine for now but may not be the right solution for the long term. Is there a problem with the widget or is it operator error?

Thanks!!