Did you create a custom page type in Montezuma? If you will post a link to the problem page, I can take a look, but more than likely it’s a problem that can’t be easily fixed.
The developers of Montezuma have decided not to continue updating the theme because WordPress has required theme developers to support the Customizer option, where all theme options are supposed to be implemented. Montezuma’s developers have decided it would be too difficult to change the theme to follow the new guidelines, so no new updates have been issued in over two years. Some users (including myself) have changed their sites over to another theme (I like Iconic One as a good substitute), but others still continue to use Montezuma, hoping that any future WordPress updates won’t cause the theme to stop working.
It’s too bad, because Montezuma was the one theme that was so easily customizeable in every aspect.