Blue triangle, watch shutdown

My Garmin vivoactive 4S had a blue triangle briefly come up on the screen. It now won't reboot. I have tried following the garmin steps after a forced shutdown, but nothing is working. I have tried:

1. Holding top power button for 30 -40 seconds. Nothing happened

2. Plug into PC and load garmin express. It couldn't detect a USB as there was no power output from the watch. 

3. Charging it up. No power/connectivity after this either. 

What do I do?