Distance between arduinos

I have tried to look at your working and non-working Receiver programs side by side but I can't figure out the rationale for any of it. Meaningless names like EU and CR don't help.

Can you provide a "walk-through" description of how the working code works - i.e. what each part does. And then do the same for the modified version.

As you have not posted a second version I am assuming there is no change to the TX code.

What version of the RF24 library are you using?

...R
Simple nRF24L01+ Tutorial