[Plugin: Jetpack] Infinite scroll doesn't seem to load *at all*…

Hi,

I have a test site at https://dearjackalope.com/juliaproblems which has the Jetpack Infinite Scroll plugin switched on – this should apply to both the homepage and the Julia Reads page (for which I will need to add a Masonry callback – one thing at a time, though!)

However, despite the fact that I have added theme support to the functions file as per the documentation and checked the ‘scroll infinitely’ box in the Reading settings, the plugin doesn’t appear to be loading at all on any of the site pages – it’s as though I never switched it on, but it’s definitely activated. It’s not that it’s loading some JS in the header or footer that’s targeting the wrong selectors or anything – there’s no sign of it (or indeed anything Jetpacky) anywhere in the code of the page.

I have already tried switching off all other plugins, and tried out Twenty Ten, Twenty Eleven and Twenty Twelve themes in place of my custom one, and nothing. It’s not generating any code in the loaded page at all. I’ve never had a plugin behave like this before!

Can anyone suggest anything? :/