Blackmarble layer not working?

Is there an issue with the tileset resource of the blackmarble imagery layer? In my own setup it does not work, neither in the Sandcastle example. Has the url been moved or does anyone knows how to get around this issue?

Sandcastle example:

Hi there,

There was an issue with how we were handling redirects to those files. I made a fix, you should be able to see it in effect shortly. Make sure to clear your cache or view in an incognito window.