ATmega328P-PU with Arduino as programmer + NRF24L01

Post a photo of YOUR connections, not the ones you are trying to copy.

That last photo also states that there is no power connection between breadboard and Arduino, but you should always have a common Ground, so connect the breadboard battery negative to Arduino Gnd (or even simpler just power the breadboarded ATMega from the Arduino during programming).

Post a photo of what you have and then people can help troubleshoot. Often someone thinks they are following an example but usually the reason it doesn't work is because they have actually wired something wrong, even though they think they haven't. :wink: