Trouble connecting Arduino Pro Mini (Atmega328, 3.3V) to nRF24L01 over SPI, receiving all 0 values when I use radio.printDetails();
Whenever you get an all zeros output from the printDetails() function you can bet you are having a communication issue between the Arduino and the nRF24 module.

Start by checking your connections.

Check your connections again, using a multimeter to ensure continuity.

Check your connections again (no, I'm not joking).

Finally add a capacitor (anything between 1uF and 100uF will do) between the VCC and GND pins of your nRF24 module: those modules are pretty sensitive to voltage fluctuations and they are subject to current consumption spikes at startup. 

Pair that with a possibly not state of the art voltage regulator (especially on cheap Arduino clones) and you end up with a non responding nRF24 module: the capacitor will provide the extra juice whenever it's required by the radio module.

This is such a common problem that I started soldering the capacitors directly onto the modules to save breadboard space!