Galaxy Note 4 - Heart Rate Monitor not working

[AC Question]

Please help!

I have started on the fitness journey (clichéd January I know) and I am attempting to use the Heart Rate function along with the, SpO2 and neither work.

By this I mean there is no "red light", or camera light to indicate that the sensor is working (and yes I know how to place my finger as my previous readings from 2015).

Interestingly, if I use other Heart Rate Apps e.g. Instant Heart Rate; the app can take a reading of my Heart rate (is this because it uses the camera rather than the sensor?).

Either way S Health can't read my Heart Rate and I have also performed the good old factory reset, uninstall and re-installing the app and my personal favourite;

1. Type *#0*# into dialler,
2. Select "Sensor",
3. Select HRM Sensor and Start

When performing this I just get a "Unfortunately,HwModule Test has stopped", same when I perform the EOL Test

Any assistance would be greatly appreciated - all the other sensors work as expected, would flashing the original stock rom, or an alternative one sort out this issue?