Xbee S2C With ZigBee firmware can't communicate in API mode

Hi, Thanks a lot for the library! I have a problem: I have two Xbee (with Zigbee firmare) and I'm trying to send data from Coordinator to Router.

If I send a remote AT command (with XCTU), the route receive the packet and the led attached to Xbee turns On/Off, so router and coordinator can communicate;
If I sand a packet in trasparent mode, Router receive the packet and I can see it with Arduino.
If I sand a packet in API mode (AT=2), the router seems to don't receive anything: I can't see it in arduino and the led attached to arduino (like the example Series2_RX) doesn't blink.
If I send a packet from router to coordinator, I can see It with XCTU, so the coordinator can receive rightly from router.

Any ideas?

Thanks!

andrewrapp / xbee-arduino