Replaced battery with one from iFIXIT.
Replaced Battery. Put on charger. Got cable symbol. Charged for 2 hours. Now have Apple logo but goes out in 5 seconds and watch does not start up.
Do you still have the original battery? If so let’s try putting in the original battery and see if the issue persists.
Thanks for the quick suggestion but I already did that as the original battery was weak but not totally gone. Same results so it must be something that got crashed in the firmware during my battery unplugging, replacement and plugging it back in. The first observation was the snake cable with the charge symbol so I left it on charge for an hour and that went away. The watch was warm as still charging. Removed the charger and the apple logo stays on for 3 seconds and then goes out. Tried the hard reset with two buttons for 10 sec and no difference. It acts like it won’t boot. The watch is no longer paired to an iphone either. I either have the Apple logo or a blank screen.
We replaced it with an AW3 about 5 months ago. So this repair is not critical. I was thinking of giving it to my grandson if I can get it working.