It's all blank!

I’ve just tried editing a form that I was working on, and although the actual form preview itself looks fine and dandy – http://proactiverehabilitation.com.au/?page_id=503&preview=true&cf_preview=CF56de166fc8384 – when I go to the edit section I see just blankness. I cannot see nor edit any of the elements I had already put in, and cannot add any other elements. I cannot create a new form, either.

I have deactivated and activated again – no dice
I have deleted, installed and upgraded – nuffin.

Surely there’s someone out there smarterer than me who can point out something simple I’m doing or not doing which is resulting in such an issue?

https://wordpress.org/plugins/caldera-forms/