Hi,
Try resetting the SMC: https://support.apple.com/en-us/HT201295.
If no luck, does the light on the power adapter light up at all? Try a different power adapter on your Mac. Try your power adapter on a different Mac. If no luck, it could be the battery. Open System Information > Hardware > Power > Battery Information > what does is say for cycles and condition? If those seem alright, it could still be the battery, or the logic board. I would bring the Mac to an Apple Store “genius” bar for a free diagnosis: https://support.apple.com/contact