The RJ45 connector has 3 wires ? I received one with 2 wires ( red Pin2 + blue Pin 6 ) ?
If that is the case contact the shop
There should be a third black wire, it’s difficult to see but it should definitely be there. Does the Pulse sensor show any sign of life when connected to an (correct) RJ45 port on an emonPi or emonTx? green led flash etc?