|Firstly you need to look at the charger, is it working? Is the little green light on the charger (if it has one)?|
If it is working fine then you need to look at the connection on the laptop (where the charger plugs in) is it loose? Is it broken?
This is something you may need to open the laptop for and get access to the the motherboard. But if you don't know what you are doing, then get someone to look at it that does.
First of all thought, check the charger (fuses etc...)