The fmuv6x bootloader is not working

Hi all.
I would like you to tell me why the fmuv6x bootloader is not working.

/dev/ttyACM0 should be recognized, but it is not recognized.

The motion was normal after the Virtual COMPORT Driver F/W was downloaded to the board for the test.

I don’t know if /dev/ttyACM0 is not recognized in the fmuv6x bootloader.

Help me.