Hello, I'm an old programmer trying to use Arduino, then my experience has a lot of limits. I'm trying to establish communication between two Elegoo Uno R3 connected the first to the RF2401 module with antenna (client) and the other one with the second module of RF24L01 (server). I checked the connnection between Arduinos and RF24L01 modules and I think that they are correct.

I'm using the RadioHead NRF24 library. Both client an server are derived by the library examples.

The client, running on COM3, seems to run correctly: init OK, setChannel OK, setRf OK, error when it wait for server response

The server, running on COM5 port, fails when executes the init statement. I am also surprised that after init failure, setChannel and setRf return an ok status. In any case it receive nothing bay the client.

I read many post but my experience couldn't make me able to find out the solution. Can anyone help me? Thanks in advance

Have a look at this Simple nRF24L01+ Tutorial. Note, however that it uses the TMRh20 version of the RF24 library

Wireless problems can be very difficult to debug so get the wireless part working on its own before you start adding any other features.

The examples are as simple as I could make them and they have worked for other Forum members. If you get stuck it will be easier to help with code that I am familiar with. Start by getting the first example to work

There is also a connection test program to check that the Arduino can talk to the nRF24 it is connected to.

A common problem with nRF24 modules is insufficient 3.3v current from the Arduino 3.3v pin. This seems to be a particular problem with the nano. The high-power nRF24s (with the external antenna) will definitely need an external power supply. At least for testing try powering the nRF24 with a pair of AA alkaline cells (3v) with the battery GND connected to the Arduino GND.