Upfront Not Working on Luke and Sarah

I've used upfront to setup some of the pages on my site. I haven't been used it for a while and I guess there have been updates on the plugins and themes recently but now, when I try to use it, it doesn't seem to work. The upfront link is on the admin bar when I'm on any admin pages, but when I click on it, it shows the page, but the upfront sidebar isn't showing and the upfront link on the admin bar is greyed out. I have already tried deactivating all my other plugins, leaving only the WPMU dashboard but it still doesn't work. Please help.