I was able to solve the problem by following these steps. Thank you for your help.
1.Short-circuit the FC REC to GND to boot in recovery mode.
2.Turn on the power, make sure it doesn’t go off, and make a USB connection to the Ubuntu 18.04 terminal.
3.Run the lsusb command in Terminal and confirm that the following log is displayed.
Bus 001 Device 004: ID 0955:7019 NVidia Corp.
4.Writing from SDK manager to USB-connected JetsonNano on Ubuntu 18.04LTS environment.
As a result, we were able to confirm booting even after the recovery mode was released.
Regards,