[Plugin: WordPress.com Stats] Doesn’t record any visitors

I’ve had WordPress.com Stats for almost a year now. I switched themes last month and all of a sudden it stopped working. The graph bounces between 0 and 1 visitor when I know I have at least 300 a day according to Google Analytics.

Is there something that might be missing in my theme that is keeping the stats from working? I’ve not added any other plugins.