Heart rate sensor isn't working properly

[chainfiree]

It fails like 8/10 times and says everytime I have to place my finger right. But I'm doing it right for sure, just like the graphic tells me. During measuring, the  graph even shows, but after 30 seconds it will fail without a result, telling me to place my finger right. When it works though, it needs 30-40 seconds.

Is this normal?

[Libb]

Isn't possible that you really put the finger wrong? It has to be on the sensor, not on camera on flash. I did the same mistake...

[Vausey]

If you have any moisture on your fingers the sensor on the S10 doesnt work, so ensure your finger is extremely dry and then its works Ok.

[lovingred2]

I'm having the same issue, but my fingers are REALLY cold so now I'm thinking that could cause reading issues/ errors... right? 

[purple-haze]

My red heart rate sensor light has stopped lighting up...
Any help appreciated...
Thanks...