cannot log in the ubuntu system, show" rebooting in 5 seconds",then restart

Autonomous Machines Jetson & Embedded Systems Jetson TX2
#1

show" rebooting in 5 seconds"in the last line,then restart repeatly.

#2

Was this working previously? Is this a new board? Was this after a flash? If you did flash, what release was flashed, and is the host a VM?