X and Cornerstone are essentially the same as Pro with the exception of the Header and Footer builder.
Anyway, I've switched to the latest version of X and Cornerstone and still, Yoast SEO analysis tab works fine.
In one of your pages, the tab goes blank when Yoast SEO is loading the Focus keyphrase.
It's weird though that while still investigating, it just worked.
I believe you did something just now?