Progression chart and metrics on the "My Fitness" page never load

The activity counts eventually load, but I get a spinner for the progression chart and the predicted performance metrics remain blank. I’ve observed this behavior in four different browsers (Chrome, Safari, Firefox, Mobile Safari) across three operating systems (macOS, iOS, Linux).

When did it stop working? Do you recall what you did beforehand? Please use if you wish to share more detail.

Thank you! I’ve followed up over email.