Raspberry Pi Revision B+ has 40 pins unlike the original Raspberry Pi. To connect NRF24L01 module to it you need to connect it as follows. This is how NRF24L01 looks like. Pins start with 1 in bottom right.
| NRF Pin | Raspberry Pi |
|---|---|
| 1 | Ground PIN 4 |
| 2 | 3.3 V PIN 1 |
| 3 | PIN 22 |
| 4 | PIN 24 |
| 5 | PIN 23 |
| 6 | PIN 19 |
| 7 | PIN 21 |