Epix 2 - suddenly died during night and not charging

I had +20% battery life going to bed. Woke up - epix2 not responsive.

Connecting to the cable (computer, battery pack, socket) - does not start charing my watch.

If I turn it on - shows 0% battery, no charging information, and in less then a minute powers down with message that battery level is critical low.

Any suggestions?

thanks