The gaming related ventilation thread!

[SERIOUSLY THOUGH*]

They're kinda fickle, and it could also be your 3DS port. They're relatively cheap to replace though, and if they don't work on your 3DS, you can try a charging pad.

How would I know if its the port? I haven't touched my 3DS in months. Let alone that I kept the 3DS and its plug charger in a safe spot.

If Nintendo has taught me anything during my life, it's blow into every hole you can find. That should do the trick.
Also that piece of advice is not recommended for most problems in life.