How are the radio modules powered? The number one problem when using those radios is lack of current capability of the radio power supplies. The 3.3V regulators on Uno, Nano, Mega simply can't supply the required current. Try adding a 10uF to 100uF cap across the rf24 power pins. I use homemade copies of these rf24 adapter modules with great success.
The tutorial that I used to get my radios to work is the simple rf24 tutorial by Robin2. I tried many other tutorials and code from the net with no success, but this code actually worked. It covers the power problem as well as some other common problems. There is a sketch (see reply #30) that will test the physical connection between the radio module and its processor.
Post photos of your wiring.