my apple watch series 2 is not charging.

my apple watch series 2 is not charging. It got discharged and I got a wireless charger to charge it. When I put the watch on the charger the apple logo comes up and then the green death snake appears and the screen goes blank and it never comes up. Even if it is put to charge for 5 hours, nothing happens. I have changed 3 chargers but status is same. Any suggestions would be welcome.