iOS 9 introduced a bizarre permissions/sharing problem: Apps that need permission (at least some of them) to access some part of the OS no longer had it. So, Camera+ couldn’t access the camera, Fantastical couldn’t access my calendars. In both cases, the apps had had permission and I’d been using them right before the update. In both cases, the app directed me to go to the Privacy part of the settings and allow access, and in both cases where there should be a list of apps that have asked for or been granted access, there was nothing. I tried wiping and re-installing Fantastical in the hopes that it would trigger a request.
iOS 9.0.1 fixed this for me. The access came back without me even having to authorize it. (iPhone 5, in case it matters)
I’m tossing this up here because I couldn’t find anything online about it. So now there should be at least one Google hit relating to it, if someone else is having the same problem.