Have you verified the steps here? Samsung smart watch will not charge or power on Is the software up to date on the watches? Have you tried resetting them? http://www.samsung.com/us/support/troubleshooting/TSG01003077/#reset-your-samsung-smart-watch
As I wrote, when my watches are on the dock, display shows 100%, so there is no problem with charging. But I can't switch them on. So I can' t control if software is up to date and I can't reset them, because they are off.
They show as disconnected. But I have new situation: I gave watches today again on the dock and they started booting, but they are non-stop restarting. Still not possible to connect them in the app.