Starting with app version 1.0.1257p (Android) and 2.1.1156 (iOS), the charts have moved from an app based system to an online or server based system. Internet signal is required in order to load activity charts in the app.
While this may seem like a step backwards, it's exactly the opposite! This new charts system opens up new opportunities for app development previously unavailable. Exciting new changes are coming, so stay tuned, Striivers!