Here are two options:
1) First, make sure that touchpad is not disabled. Try the combination Fn+F9 to enable it.
2) If it did not work, follow this one:
- Turn off your laptop
- Unplug the power cord from the laptop
- Remove the battery
- Press and hold the Power on button for 50 seconds
- Now insert the battery
- Plug the power cord
- Turn on your laptop.