The newly announced Raspberry Pi 4 is the first to sport a USB-C port for charging, and it turns out that it's completely buggered it up.
A blog post by Tyler Ward was the first to report on and identify the issue that sees the port fail to charge the device with a range of cables.
The long and short of it is that if the Raspberry Pi 4's USB-C port design had fallen in line with the USB-C Spec, there wouldn't be an issue. But it didn't. Instead, the implemented design sees it share a resistor between its two CC pins, rather than allowing them one each. Problem number one.
Problem number two is that "e-marked" USB-C cables contain a chip to manage power, and detect accessories and whatnot, so when they're plugged into the Raspberry Pi 4, they register it as an “Audio Adaptor Accessory” which means they won't juice it up.
Pi 4 co-creator, Eben Upton, confirmed the issue to TechRepublic, adding that it would be "fixed in a future board revision." For now, you can just lump a workaround, like using non e-marked cables or, conveniently, shelling out for the official Pi 4 power supply for $19.95.
Upton added that it was "surprising this didn't show up in our (quite extensive) field testing program." I guess plugging the thing in to charge wasn't an integral part of the test.