If your tablet is showing a battery symbol with a red exclamation mark when you plug it in it means that the battery is fully dead or it has become dislodged and it might require the battery to be reconnected.
First trying the tablet fully off and plug in the charger for some time. Then remove the charger and try to restart the tablet. If the red exclamation mark continues to appear, the battery might be loose and would require reconnecting.
Posted in: Tablet PC Batteries