Update 2017-10-16:
Problem solved. One should use the old View app - with the white background. I don’t have currently a link to post.
But it worked with at least two IDs.
Thanks for answering. My concern is that none of the IDs in the newly published themes worked. I doubt people are buying themes on the market without trying them out first. So I assume I am in the wrong here.
@Sujan12, we can easily figure out if it is me or everyone else. If you try anything from the market on your iOS device and publish here which ID worked, I’ll do the same. It will establish if it is my setup, or the app vendor.
This is frustrating as hell. I would expect a gread company behind a great product communicate better.
I would at least expect a link from the ID on the market to an explanation popup or page - how to use it.