Make sure that you are running v4.9 or later.
This add-on will not function properly on any version earilier than v4.9.
How to find out what version you're running
Log-in to manage your website with Pro Edition (i.e. http://example.com/sohoadmin)
and look in the bottom right corner of the admin tool window (ie. in the footer).
How to update your version
If you're running v4.8.x or earlier than you've got to first update to v4.9 via Fantastico.
Once you're on v4.9 you can update to the latest build using v4.9's built-in Software Updates feature (Main Menu > Webmaster > Software Updates).
