Atahualpa Category Archives navigation issue

When a user selects a category, to see past posts, only the last 4 or 5 entries show, and there’s no way for them to browse entries previous to those.

Ergo, a huge amount of my content is really hard to find.

Just to check, I loaded another theme, and the category entries were all available via <previous posts> type navigation. It’s just the atahualpa theme where I seem to be missing previous/next navigation on the category pages. I’m not sure how to fix it, but any suggestions would be fabulous as I love, love, love this theme.