[xvf22]

Each of the USB-C ports needs a controller and if any of the four have an issue the computer will not charge.

[adrianN]

One of the USB-C ports on my work laptop recently failed but the machine still charged from the other one.

[xvf22]

Was going by this [1] which seems to show that if one of the charging ICs goes bad it can cause the rest not to work. This is probably one of many failure mechanisms.

[1] https://youtube.com/watch?v=MY8LlHfK9ZA

[saagarjha]

I believe MacBook Pro has two Thunderbolt controllers, one for each side.

[Jdam]

The USB controller is unrelated to USB power supply.