G-Shock was conceptualized in 1981 by Casio engineer Kikuo Ibe when he accidentally dropped and broke a pocket watch given to him by his father. The G-Shock was conceived as a watch which would have "triple 10" resistance, meaning it would have a battery life of 10 years, have a water resistance of 10 bar and could survive a fall of 10 meters
I finally found the solution: reset the watch by the AC contact being connected to the back of the battery by metal tweezers. So the general suggestion is that these watches are computers, they can get confused, can crash, and need a reboot to resume normal operation. To reboot a G-Shock, use the AC procedure as if you were changing the battery.
KpThBD.