I've read the thread about themeforest themes causing issues with AJAX, but I think my issue is slightly different. I have a themeforest theme, which worked fine with AJAX enabled, but suddenly AJAX has stopped functioning. The forms now work as if AJAX is disabled and I can't find the issue.
I've tested with all plug-ins disabled, any additional JS scripts have been removed. Funnily enough it does work on my local installation with a current version of the theme, Gravity Forms and an imported database.
Here's a link to one of the forms: http://www.migrationangels.com/australia/skilled-visa/assessment/
I'm not quite sure whether it was a theme update, plugin update or something else which triggered the issue.
Any ideas what it could be?