AppleTV 4K - Flashing White Light of Death

Hi - curious if anyone can help. I have a relatively new (within 6 months) - AppleTV 4k that starting flashing a white light, and now is an interesting black box that flashes and nothing else. It isn't the HDMI, nor ethernet, nor power supply. I've tried the trick with the remote (menu and home) - no joy. I am out of ideas because there is no way to connect it to my computer (as far as I can tell). The only input/outputs are Power, Ethernet and HDMI.

Any ideas?

Thanks