Why does the Apple Watch Workout stop reading my Heart Rate?
I've been having this issue since Watch Series 3 and Watch Series 6 a few months later (on WatchOS 9 is when it did this FYI). When I finish charging and I start a workout to go for an Outdoor Walk, my heart rate stops working.
It begins from 115 BPM my normal heart rate on a brisk walk down to 90 BPM and starts circling to find my heart rate. It only works again if I have Heart Rate app on the watch and check my pulse once it stops working. It blacks out and no Zone Recording is completed for a length of my exercise of 30 minutes.
Apple Watch Series 6