i2c probe happens only alternatively
The PN7120 is normally in a low power mode.  In the datasheet it says that the chip has "wake-up on address only".  You need to first send it just an address only I2C transaction to wake it up, and then quickly send actual I2C transfers before it goes back to sleep.  Sending two i2cdetect commands close together simulates this.  See this thread for someone who was having a similar problem.