How to burn bootloarder in nano board?
1. Open the Arduino IDE, then select the board Nano and connect the Nano which is work normally.
2. Select the Arduino ISP sketch

3. Choose the nano board and the port COM16

4. Compile and upload it

5. Choose programmer : “the Arduino as ISP”

6. Connect the Nano which is not work to the Nano which is work normally at the list:
Nano———-Nano（not work）
10————RST
11————11
12————12
13————13
+5V———–+5V
GND———–GND
7.Click “Burn Bootloader”

Note:
For Mac Computer, please kindly download the Arduino IDE Mac OS X from https://www.arduino.cc/en/Main/Software