Ever since the iOS app update to 3.5 intensity minutes is no longer an option to view. It use to be one of the data squares on the summary page and there was an option to make it as another snapshot, but it is no longer there. Did they completely remove intensity minutes from the app?
Still there for me. I've had data fields vanish before. To return them I've just had to close out of the app (swipe up in app switcher) and re-open, and it re-appears. Maybe delete the app from your phone and re-download it from scratch from the app store? That fixes most other bugs in most other programs.