How? Did you use one of the example sketches that you downloaded with the library? I suggest you try one of those - the documentation explains more fully, the “min” one uses the absolute minimum number of options that give a working demonstration, while the “max” one gives an example of every API call.
There is a problem with JeeLib, that didn’t show up during testing, which has caused lock-ups and resets - is it actually resetting and the zero value is a result of that?
The calibration for voltage and current should be the same, but the phase error correction values are substantially different, and using the values for the DS sketch will give an error in the real power value reported.
Are you implying that you are using the serial connection for the data output?
If you are then you don’t need to transmit the data using the RFM and you can comment out all the RFM functions beginning RF12_. That should remove any difficulties arising from JeeLib.