My 5X just stopped taking a reading. I've charged the battery to 100% and restarted the watch with the same problem.
I could scroll down to the widget and then next to the heart symbol it would say, "---" and then "Measuring" and then back to "---". I take off the watch and then I noticed that the green light doesn't turn back on.
I would go into an activity and the watch would never try to pickup a heart rate.
