[Plugin: Subscribe2] subscribe2 widget not showing the form

I just installed the subscribe2 plugin (version 8.4, which has the widget included now), enabled the widget in the Subscribe2 settings per the instructions, and put the widget to display the subscribe form on my home page, but it doesn’t display any form! The title of the widget area and the text I enter before it shows, but no form at all. Is there something I forgot to do?