Here is an Apple articles for troubleshooting charging issues:
If your USB-C power adapter isn't charging your Mac laptop - Apple Support
Make sure to disconnect all external devices in case one of them is causing a problem. Also make sure to connect the charger directly to the laptop since adapters/docks/hubs may not allow the full power of the charger make it to the laptop. Try using another USB-C port especially on the other side of the laptop if possible.
If this does not help, then you will need to have Apple or an Apple Authorized Service Provider examine the laptop (take the charger and charging cable as well) to provide you with a repair estimate.