PN532 doesn't read the tags

Hello,
I use an arduino mega and a reader/writer PN532. My problem is the following: the reader/writer doesn’t authentic more blocks of a certain sector, or if it is authenticated at the following operation (read or write) is not authenticated. I do not know the reason for this. I changed several times the access key but nothing. The connections are for the use of the standard i2c.

Arduino Mega2560 PN532

GND---------------------GND

VCC---------------------VCC

SDA---------------------SDA

SCL---------------------SCL

D3-----------------------IRQ

Help me please!!!! I need help desperately :( :(