Xbee S2C Issues

Hello all,
I have Xbee S2C and I am having an issue with these xbees. I am trying to run these xbees on arduino in API mode but I can not. The point is that the arduino code is the code that I could run in arduino six month ago but now it does not work anymore. Is there anyone who knows what the problem could be?
Thanks

What is the full part number for the XBee modules you are working with?

Hello,
XBP24C if you ask that. And here is the code that I have worked with. As I said it was working 5 month ago, I really dont know what was happend. Thanks for your help again.
#include

XBee xbee = XBee();

uint8_t payload[] = {0,0};

// SH + SL Address of receiving XBee
XBeeAddress64 addr64 = XBeeAddress64(0x0013A200, 0x418DAC91);
ZBTxRequest zbTx = ZBTxRequest(addr64, payload, sizeof(payload));
ZBTxStatusResponse txStatus = ZBTxStatusResponse();

void setup() {
Serial.begin(9600);
xbee.setSerial(Serial);
}

void loop() {
xbee.send(zbTx);
delay(1000);
}

XBP24C is not the full part number. The full part number is on the white label on the shield side of the XBee. It will be something like XBP24CZ7SIT-004.

Oh, okey sorry for that. The full part number is XBP24CZ7UIT-004.

I would tend to think you don’t have the AP and AO commands set correct. Generally Arduino code wants API mode with Escaped characters.