Brought a new Fenix 6 due to its claim of OHR function in swim. Made sure it was engaged and tried the 1st pool swim today. To my surprise, no heart rate data was recorded. All swim data was normal as that in Fenix 5. In another word, although I noticed the heart rate LED was on in the Fenix 6 and was off in the Fenix 5, the recorded data was same. What went wrong?