Directory Listing Ratings Not Working

Hi,
We're using the Directory plugin on a multi-site install with domain mapping. I've configured most things I need for now, but I'm struggling to get the ratings to work.

I've copied the "single-lisiting.php" template to my themes folder and edited it a little to allow anyone to rate and I don't allow people to register on the site as such.

Even before I did that though, the rating number never seems to update? Is it done periodically or if I voted now, should it show immediately?

Here's a the test listing I'm working with http://www.modeltrainsonline.co.uk/listing/expressway-models/

Any help would be greatly appreciated, as I don't really want to go any further until this feature is operational.

Thanks in advance

Justin