My Apple Watch is not detecting heart rate when I run. Seems to do fine all other times. What s the solution?

Unfortunately this solution didn't help. I did everything what you recommend but still I don't see "heart rate" in run and walk activities. In other like tennis or yoga "heart rate" works very well.

Turn off workout power saving mode,this turns off the heart monitor during workouts.

Ok, I found reason. In workout should be turn of f:POWER SAVING MODE