An Automatic timepiece charges by the kinetic energy of your hand, meaning that the power reserve will stay full as long as you wear the timepiece through out the day.
The reason why it has stopped working may be due to the fact that it has simply ran out of power. A fully charged timepiece will hold for 40 hours straight.
To charge your automatic watch you can either put it on your wrist and walk for a a few minutes, or it can be charged manually while turning the crown clockwise.
When fully charged, the power reserve indicator located at 12 o'clock on our Venice Automatic models should point towards the right.