If you didnt hear last month, Google and HP had some issues with their HP Chromebook 11 chargers where they were causing the device to overheat and become damaged. At that time they advised to stop use of the chargers and use any other microUSB charger until a resolution was created. Alongside that HP Chromebook 11s were being recalled and pulled off the shelves everywhere.
Today, there is a solution and it involves you filling out a replacement form and putting in key information such as your serial number and mailing address. After its all processed they will go head and send you out a new charger. If you are unsure you need your charger replaced check out the FAQ about the HP Chromebook 11.