Make sure you’re using the top USB-C Port on the left side of the device for data/video. Other ports wont work for 4k. Also make sure you only have one monitor hooked up when you do this.
The Cable I Used: https://www.amazon.com/gp/product/B0163LN18M/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
The Wacom Cintiq Pro 16 gets stuck at 1440p when using the Wacom Link and wacom support says you can’t use a Wacom Cintiq Pro 16 in 4k if you’re using the Wacom link. They are wrong, here is how you do it.