Good point kitcorsa.

Actually the whole attributes issue looks like it was a bit of a red herring. I know why I saw that as the issue but it turns out it is coincidental. I was adding attributes when I noticed it and letting ceon uri mapping generate uris as I was doing it. So, all the items with new attributes also had URI mapping.

If I let the mod re-write any product then that means that that product is not added.

Must be some configuration issue on my site because I just don't see how this is the case with all the sites using this mod.

look in 'Emergency Equipment' you'll see a blank product with no attributes - also disfunctional.