Try a hard restart first.
Removable battery:
1. Unplug AC power adapter
2. Remove battery
3. Hold down the power button for more than 30 seconds
4. Plug everything back in
5. Power on the laptop
Non-removable battery:
1. Unplug AC power adapter.
2. Locate the battery reset pinhole on the bottom of the computer.
3. Insert a small paperclip in the battery reset pinhole. Hold the reset button for 4 seconds.
4. Let the computer sit for 5 minutes with no power.
5. Connect the AC adapter and power on the system.