telemetry temp on main screen?

Help!!!!!

New to Devo 10,......setup in my racing boat.
Want to get the receiver voltage back to my transmitter.
I know how to do by few tutorials on U tube by changing settings in the Menu. activating the voltage and then going to see on the screen after it is binded to receiver. but nothing comes up in Function menu ; sensor view 'Voltage it always just says "Inhibit" in all feilds.
Do I need something else on the receiver end?

I can't get the voltage telemetry on the devo 10.
setup the transmitter correctly I think. Do you need sensor or something receiver end?
I am only running receiver and two servos.
Do I need to load the latest firmware?
I thought you can get the battery voltage via receiver with telemetry?
Thanks for any assistance.
Happy with this radio otherwise.