Thank you for reaching out. Are you referring to the lights no longer blinking on the back of the watch?
I am having the same issues, have gone though all the boards and tried everything on the forums. My s3 is a SM-765A
Battery drains extreemly fast and none of the senors work. Sensor hub shows test failed.
I was having this issue since the beginning of this year. After a lot of research and trying everything I've found on Internet last month I sent my watch to a Samsung service center.
They replaced a circuit board and now my watch is working perfectly, but it costed one third of the price of a new one.
I still think this problem was caused by one of the software updates, probably overloaded some circuit.
Honestly I don't think I'll trust Samsung again when looking for a new one...
Hope this can help other users!!