Which pins did you use on the MEGA2560 for the SPI signals (MOSI, MISO & SCK)?
Have you tried the CheckConnection sketch from post #30 in the nRF24L01 tutorial here:
Which pins did you use on the MEGA2560 for the SPI signals (MOSI, MISO & SCK)?
Have you tried the CheckConnection sketch from post #30 in the nRF24L01 tutorial here: