|Have you, or is it possible anyone else has....|
- dropped this netbook computer, or dropped anything on it, or subjected it to a physical jolt otherwise ?
- spilled liquid on it, or exposed it to liquid such as rain, or sprayed it with liquid ?
Has there been a power failure event while the computer was plugged into the AC adapter ?
A nearby lightning strike ?
There is no reason your keyboard would not work other than it's damaged or your Lenovo IdeaPad S10-3c is otherwise damaged.
There is nothing in your User Guide that disables the keyboard.
IdeaPad S10-3c User Guides and Manuals
Try a USB keyboard for the time being.