Neil, thank you so much for answering. I deleted and reinstalled the app
and now the content is visible. It seems that I have to delete and
reinstall every time I change something in cards and layouts. I'll just
keep doing so while waiting for the release next week that Nathan
mentioned, and if it doesn't work properly by then I'll start a new
thread with screenshot.
I have the same problem, the preview app is not showing anything. It
worked fine when I still had the default layout, but after I created
cards and layouts it is just showing a blank white screen. I have used
the same layouts, cards and grid as in the tutorial video. Anyone who
knows what might be wrong?