Master node LoRa (SX1278) and Slave Nodes (SX1278) Restart Issue

We have built 5 slave nodes (Arduino Nano + LoRa SX1278) and one master node (Raspberry pi + LoRa). In the first attempt, after flashing program, it run smoothly.

When we shut downtown master node and sensor nodes, then it start again, master node send request to slave nodes but sensor nodes doesn’t give the response.

We are serial printing data, not using the display.

Please help me resolve this issue