[quote]Sometimes the SCK pin is not connected[/quote]Now why would that be? It obviously can’t work if the SPI clock pin is not connected, so you really need to be more clear.
The confusion may be due to the SS (Slave Select) of the SPI protocol defaulting to different pins on an ATmega (PB2, Arduino Digital Pin 10) as opposed to the A-Star (PB0, Arduino Digital Pin 8).
However, the code you most recently posted (RF24_receive.ino) does not agree with your wiring diagram. The receiver code identifies CE as Arduino pin 9, and CSN (SS) as pin 10, whereas your wiring diagram for the A Star shows connections to Arduino pins 7 and 8.
It should be obvious that the code and wiring will have to agree AND be correct, if this is ever to work.