Problem with default sidebar in Selecta theme

I am using the Selecta theme and have three widgets running in the default sidebar. The sidebar appears in the appropriate place on every page of the site, except the landing page where posts are displayed. On the landing page, the sidebar appears below all of the posts. Does anyone know what the problem is?

The site can be accessed here: https://fuerzatucson.wordpress.com/.

Thanks for your help!