MacBook Pro (15-inch, 2018)

Try an SMC reset and Nvram reset.https://www.avast.com/c-reset-mac-pram-smc Run through some of this also.If your USB-C power adapter isn't charging your Mac notebook - Apple Support

You can always run the Apple Diagnostics to see if any hardware issues are detected.

If this repair was performed by Apple or an Apple Authorized Service Provider, then you have a 90 day part/repair warranty so take the laptop back to have Apple or the AASP check it out and make it right if there is a problem.