@ruslancc Unknown but I have fixed that now.
It could be that the M5Stick can not provide enough power for the heart rate monitor.
You could try connecting one of these
https://m5stack.com/collections/m5-accessory/products/grove-t-connector-5pcs-a-pack
alt text
between the Stick and the heart rate monitor and use the other connection to provide an additional power supply for the monitor.