Try the following and see if it will start to charge.
1. Unplug your charger cord.
2. Remove the battery.
3. Press and hold the "Power" button for 30 seconds.
4. Now replace the battery and the power cord.
5. Do Not turn on the device, just see if it will charge.
If it will charge while off, but not while on, then the problem is probably the charger cord. If it still won't charge at all, no matter if off or on, then it is probably either the battery, or the charging circuit (which could mean replacing the motherboard).