UserAgent: Mozilla/5.0 (X11; CrOS x86_64 8172.62.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.106 Safari/537.36
Platform: 8172.62.0 (Official Build) stable-channel samus

Steps to reproduce the problem:
1. Boot and sign into Pixel
2. Connect adapater to displayport cable and USB C port
3. Connect displayport cable to 30" (2560x1600) monitor input

What is the expected behavior?
It works.

What went wrong?
ChromeOS says "Extending display to HP ZR30w", but there is no output on the display and it quickly goes into power save mode.

Did this work before? N/A 

Chrome version: 51.0.2704.106  Channel: stable
OS Version: 8172.62.0
Flash Version: Shockwave Flash 22.0 r0

Same cable/monitor worked fine with the native displayport output of an HP chromebox.  Same cable/adapter/chromebook works fine with a 24" (1920x1200) display).
Adapter is: https://www.amazon.com/Vtin-Charger-Adapter-Macbook-Chromebook/dp/B01AAK5FRC