Shopify Widgets app not working. by Rob Nanya

Shopify Widgets app not working.

I go to admin dashboard > apps > Shopify Widget > Embed a Shop.
Select collection > Next

Click preview and all I get is an empty lightbox and the only thing that shows is the X to close it.
The collection has two products in it though so something should show, right?

I'm not even trying to embed this on my website yet.  What's going on?

Should mention I'm using 14-day trial, not sure if that has anything to do with it.