Same problem here. Threads on other sites suggest it's a drive space issue but I have over 200gb free. This is very frustrating. Same result with other versions of iOS. Next I am going to try to download an Xcode beta version to see if it works.

Popovers are meant to be shown as sheets on iPhone. If you run the app on an iPad or a Mac if its a universal app, you will see it display as a small overlay as the name suggests. Hope this helps.