You should have a 10uF or similar electrolytic capacitor across the +Ve and ground of the NRF24L01 module, where you plug its wires into a breadboard for example. Try that first.
Electrolytic capacitors are polarised so remember to get them the right way around.
Are you powering both NRF24L01+ from the Arduino? If so, that's almost certainly the problem.
I've just been playing around with one NRF24L01+ and I had to connect it to a separate supply to get it to work. With two NRF24L01+, you'll definitely need a separate power supply.
Also, the NRF24L01+ runs at 115200 baud which is quite fast and you may have to be careful how you handle the I/O between them so that you don't lose any characters due to an overrun buffer.