You could start here:
I’m assuming you have the connections correctly identified, and you restarted the emonPi front end (NOT just rebooted the Pi) after you had connected the sensors - because they are only checked and identified when the ATMega 328P that’s the “emon” part of the emonPi starts up.
The safe way is to do a controlled shut-down of the emonPi, remove power, then power up again.