Jetson TK1 no longer powering up

I have recently started to use the Jetson TK1 dev board. Initial startup everything looks fine, logging on to Ubuntu all looking good. I then went to upgrade Ubuntu - the installation was running well, and I left the TK1 for a few minutes while the installation was taking place.

When I came back to the TK1 it was powered down. I switched on the restart button, the fan power up for a few rotations, then stops. The LED power light switches on for a second then switched off. I do not see any boot screen.

I did not touch or change any connections during this time. I was using an electrostatic mat previously while connecting power and HDMI, keyboard, mouse to the TK1.

Has anyone come across this problem before?

What was your upgrade? Via or JetPack? Just normal package update (“sudo apt-get upgrade”)?