lastfmSidebar add-on is blank?

I installed the lastfmSidebar, restarted Songbird, and loaded the add-on into the sidebar. While the sidebar shows that the lastfmSidebar add-on is turned on and supposedly functioning, it displays a blank area - no songs, list, or anything besides the Refresh button.

I am logged into Last.fm through the Songbird Last.fm extension, and scrobbling is enabled. I am using Songbird 1.0 for Mac.