I'm calling you here because you already know my site reasonably well and have always been able to help with my most substantial issues.
Checkout pages aren't being displayed. Here's an example (you'll need the credentials I've sent through WPMU's contact form):
I've migrated to Cloudways, it was working on GoDaddy though. According to the guys at Cloudways, "some table seems to be missing in the database", though presumably they've already restored all of it.