I set up 2 Unos with rf24 radios, sender with pot and receiver with servo. I only changed pins (CE, CSN, servo pin) to test your code. It works fine. I can adjust the position of the servo with the potentiometer.
How are the radio modules powered? The most likely cause of problems with rf24 radios is lack of current capability of the power supply. I use homemade adapters like these with great success.
Carefully check your wiring.
Check out Robin2's simple rf24 tutorial. He discusses the power problem and some remedies. His tutorial is what I used to get my radios to work. There is a sketch to test the physical wired connection between the radio module and its processor (see reply #30).