We just bought 2 of these last week, 42mm and a 46mm. I have had no problems with mine. My fiancee has had nothing but problems. Can't get the heart rate monitor and the Always on display to always work. Someone said they shaved their arm and we thought hey that could be it. Then we thought about it for a minute and said maybe it's because his arm is tattooed to his wrist. He switched it to his other arm and sure enough, IT WORKS!! Now he wears it on his other arm.
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