Sorry,
that's wrong!
I have a Iphone4 und die GC app since a few years. (Version 4.6) I got the premium membership a week ago. And a log in / log out and restart of the app didn't work. No premium features!
I hat to delete the App und reinstall it from the appstore. Not easy, but it works!
@ Groundspeak: Please fix this bug!
Greetings from Germany
Zivi im Dienst