Do you hear the "ding" sound when the charger is connected?
Try an SMC Reset.
Try unplugging the charger from the electrical outlet for a minute to reset the charger's internal circuitry.
Plug the charger directly into the laptop since multi-port adapters, docks, and hubs can prevent the full power of the charger from reaching the laptop. Also try another USB-C port especially on the other side of the laptop if you have four ports.
Here is an Apple article for troubleshooting charging issues:
https://support.apple.com/en-us/HT204652
If none of these steps help or you find only some USB-C ports work, then you will need to have Apple or an Apple Authorized Service Provider repair your laptop under warranty.