MapBox maps not showing up on custom site.

Hi there StoryMap team.

First off, I wanted to say thanks for a great tool. This is just what I've been looking for. It's awesome!

I have created a StoryMap using a MapBox base map, which works fine when using either the preview option, or the embedded link:

http://cdn.knightlab.com/libs/storymapjs/latest/embed/?url=https://www.googledrive.com/host/0B6ho0vbPBQFpRlBLLXVLNC0tcEU/published.json

However, when creating a custom site using the example shown on the Advanced page, the base map defaults to the monochrome Stamen map. Any thoughts on this? I have a test site for you to view: http://maps.lifeandlandscape.ca/maps.html

Thanks for your input.

Andrew