When the calendar's on the home page, the CG script doesn't make the latest date a hyperlink because it would just pointlessly link to the same comic page you already see. Instead, it gives the date a white background to indicate that it's the latest page.
I think your use of the include file may be throwing off either the browsers or the script, causing the supplemental pages to display this "home page version" of the calendar. If that's the case, then copy-pasting your navigation code into each separate HTML file should fix the problem.
However, I don't see this problem as being significant, as readers should already be aware that the latest comic's on the home page, which can be easily be accessed from any page on the site by clicking on the Chainmail Bikini logo, or by clicking the "Latest" button located above and below every comic page.
Like, there's no health meter or points, because everything's just cool. You don't have to worry about it. And when you come to a boss at the end of a level, you just make friends with them, and then you all party together.