I have created and installed a preview app and have read some of the other comments here on this topic. I have added .article files to my Top Level collection and published. No update bubble shows up after closing and opening the app after a few minutes. Do I need to click the preview icon in the upper right corner of the Web Portal each time I want to preview changes on the device? I have tried that also, with no resulted update. If I delete the app and reinstall, my updated content then shows.
Thanks for your help, however, the problem of the Preflight App not updating on my device (Samsung Galaxy Tab E) remains. I guess, I do not understand what you mean with 'background and foreground the app'. Sorry, I'm a newbie.
I have now unplubished all my updated content (the 'default' collection cannot be unpublished). The Preflight App still shows the original content, and I see no 'update bubble', or anything else to indicate an update is available. The only thing that works is deleting the Preflight App from my device and reinstalling it from Google Play. That's a bit tedious. What action is required to 'background and foreground the app'?