Watch won't turn on

My watch screen turns on when I put it on the charger to show me that it's charging. It displays perfectly fine, but won't actually turn on for use.

When I take it off the charger, it's just dead. Won't turn on, won't do anything.

I've taken it completely apart and haven't seen any visible damage. Any ideas what could be wrong and how to fix it?

It honestly hasn't gotten that much use in the year that I've had it, so not sure why this happened all of a sudden.

Thank you.