Lora Device receive ACK After that receive one data otherwise can not receive

Hi everybody,
I use i-cube lorawan software with st microcontroller. Firstly, i change the device address in controller and send data to server from the device. I can not receive the ack. But I tried send random data to device from loraserver, device received that. After this operation device can receive the ack when send data. What is the resion of this problem? How can i solve it ?