According to several posts on Reddit, it appears that some users are discovering that when their laptops are shutdown, the laptop is unable to charge. It is a very specific scenario so not all users might experience it. Basically, if your laptop is unplugged and you shutdown and then plug in the MagSafe charger, it will make a ping sound and the connector’s LED will flash in a continuous loop and won’t charge the laptop.
This isn’t an issue if your laptop has been continuously plugged in and if your battery is above 80%, so like we said, it’s a very specific scenario in order to replicate this issue. This also only seems to affect the 16-inch MacBook Pro when using the 140W charging brick that comes with the laptop, but interestingly enough, if you use USB-C to charge it, then this isn’t an issue.
Also, if you plug in the MagSafe charger before you shutdown, this won’t be a problem either, so those are temporary workarounds. Some users claim to have taken the laptop to the Apple Store and have been told that Apple is aware and is investigating the problem, while some were offered replacements.