This is probally what your missing in showproduct.php
Code:
Content visible to verified customers only.
There is also a language string most likely as well so all things you want to check out.
The point I am making though in on showcat where products are listed we only grab sold or approved products. If your cron scripts have been updated and set expired ads to 4 meaning new ones not old ones already expired then they are not shown on the ad listing.