Hi there,
For some reason the x parent URL part did not work on your hosting service which is the main section to start work with the Cornerstone in the new version.
I went to X > Cornerstone and changed the path to builder and now the link works and shows the builder:

But there is now another problem which is that the Cornerstone reverts back to Skeleton mode for some reason.
That is not the case for new pages as I added a new test page and it worked ok:
http://www.fireleaf.co.uk/test/
Kindly double check the pages that you have to find why this is happening for them.
Thank you.