Apple:

A limited number of Apple USB-C charge cables that were included with MacBook computers through June 2015 may fail due to a design issue. As a result, your MacBook may not charge or only charge intermittently when it’s connected to a power adapter with an affected cable.

Apple will provide a new, redesigned USB-C charge cable, free of charge, to all eligible customers. This program also covers Apple USB-C charge cables that were sold as a standalone accessory.

Got a MacBook? Click here and see if your cable is eligible for replacement.