First, check if the battery is charging by plugging your Chromebook into a power outlet. (Usually, you'll see a light on the side of the computer turn on.)
If your Chromebook is charging, let it charge for at least 30 minutes.
If your Chromebook still isn't charging:
Check if the charger or adapter cables are completely plugged in, both to your Chromebook and the wall.
Make sure that the power outlet is working.
Unplug your charger from the wall and your Chromebook.
Plug your charger back in to your Chromebook, then the wall.
Charge the device for at least 30 minutes.