It's dead Jim.
Walked away from my Macbook Pro 15" 2018 for a couple of hours. When I came back, it was completely dead. Power button does nothing, No fan, no sound, no keyboard light, no touchbar light, nothing on screen. It is as if someone took the battery out of it. I verified that the charger is working, and indeed, I have a second charger and used that! Again, nothing. Zero. Tried while plugged in to the charger, tried while unplugged from the charger. Nothing.
I've tried the 'start in safe mode, reset NVRAM' things. Nothing.
Any ideas?