NX cannot boot today

My NX run well last week. But today, I plug in the power, and the Green NVIDIA appeared in my Screen. Then, turn to black screen. My screen shows there is no signal. And the light still bright in my NX board, and there is hot on the fan.
What’s the problem? And how can i fix it?
Thanks !

It wouldn’t be unusual for the system to be working normally, other than the GUI not working. Can you still ssh to the NX? Either way, you’ll probably need to post a serial console boot log. See (NX and Nano use the same dev kit carrier board):