According to MacRumors, some 16-inch MacBook Pro users seem to have discovered a common problem: When the device is turned off and the screen is closed, the MagSafe 3 charger cannot provide the expected power. As a result, the user cannot charge normally, and strangely, the MacBook Pro battery cannot be charged at this time.
When the MagSafe 3 charger is removed, the battery resumes charging, but the user cannot charge other devices through the MacBook Pro charger. When a fault occurs, the indicator of the MagSafe 3 connector is not green but flashes amber. Some users contacted Apple for after-sales support and achieved varying degrees of success. It is not clear whether this is a software or hardware problem.
So it’s not just me then! I have the EXACT same issue. Went to the genius bar and they tested with a cable and charger that they have and it still had the same problem. They said they would order a new 140 watt charger for me to see it would fix it but said most likely it’s a firmware issue but didn’t really provide any evidence for such a thing. I went home and the next day I get a call from Apple. Someone was calling me to follow up and they asked me a bunch of questions and provided instructions to run a special diagnostics program. After I did all that they said they want to take my MacBook and its charger back and that they would give me a completely brand new MacBook as soon as they get one. I’m still waiting for that but that’s where I’m currently at.
There are users on the Reddit forum detailing the situation when this problem occurred. When the MacBook Pro is closed, the MagSafe charger indicator repeatedly flashes amber and is accompanied by the typical macOS charging sound. The steady orange indicator light means the MacBook is charging, and the green light means it is fully charged.
If the MacBook Pro is connected to the MagSafe charger and then turned off when the MacBook Pro is turned on, MagSafe will continue to charge the Mac as expected. This problem only occurs when MagSafe is plugged in when the Mac is turned off. The flashing amber light also means that it is not working properly, and this problem cannot be solved even after MagSafe is restored. And not all 16-inch MacBook Pros will encounter this problem, so it is not clear whether this is a firmware or hardware issue.