So I have the "Free Version" and this looks like one of the most open areas for discussion of any problems with this plugin. Maybe someone can help.
to add a post, the authors website says:
* Can I place auctions in a post or page?
Yes you can. Just follow these steps -
1. Write a draft for your post or page and save it in WordPress.
2. Add an auction under the WP Auctions admin area.
3. At the very bottom of the panel you will see an option called “Show auction in AJAX Popup:” select “No” and specify the post or page URL you just saved in the field provided. You can get the URL by looking at the absolute path of your post, for example http://yourblog.com/my-post.
4. Go back to your saved draft, below the write area you will see a window that says “Insert Auction”. Select your auction and click “Insert Auction”.
5. The short code is as formatted as such: [ wpauction id="Auction ID" / ]
6. That’s it!
Points 3,4 and 5 don't exist in my plugin (I just downloaded and I'm on the latest version of WP)
My guess is that it doesn't work without paying for it.
I have tried to enter variation of the short code to make my auction appear, but it doesn't work.
Then I found this http://wordpress.org/support/topic/273658?replies=5
is it true that the free version of your plugin does absolutely nothing?