issue with advertising banners not showing up

I’ve just purchased this template and running it through its paces. So far, so good, It’s a little buggy in places which I’ll probably detail at some point but overall is a decent template. I’ve got it setup and running pretty much all the way.

Here is the present issue I am finding. I have enabled advertising. For now, just the 4 sidebar 125×125 ads. Customer purchases an ad block. Customer looks in their account under premium advertising and sees their order there. Customer has added their banner, chosen it under the order and added a link. So all seems good there.

Banners shows up in backend in the banners section and the campaign shows up under the campaigns section with a ticking expiration date. So all seems good there.

Banner is not showing up on front end in one of the 4 advertising slots. However, if you look at the purchase advertising page, one of those slots is now gone as it should be. So everything matches up far as I can see, and as detailed here, except the most critical part of this exercise which is the banner actually showing up.

Any ideas on what gives here?