How to get documents to open in iWork on iOS 11?

I have a simple app that lists Pages, Keynote and Numbers documents. It is based on the sample code "DocInteraction". It works fine, but not if I try to open any of the contained documents via the share menu "Copy to Numbers". When tapping that, nothing happens.


This is for all iWork documents as well as PDFs for iBooks. It worked on iOS 10. Did I miss any changes? The sample code is still available, so I assume it should be working.


I'm thakful for any helpful advice.