VR preview is NOT activated in OSX setting

Hello, anybody succeed to run SteamVR with HTC Vive on Mac Pro 5,1 with NVIDIA graphics card?

I just installed 4.18, and made an empty project following below link.
https://docs.unrealengine.com/latest/INT/Platforms/SteamVR/QuickStart/2/index.html

but the VR preview button never activates. (photo attached)

Does the VR preview button only activates STEAMVR is opened and working properly?

I am using NVIDIA graphics card in Mac Pro 5,1 with Vive. Unreal supports this setting? (Since I have some issues in steamvr with Vive in my setting)
When I run SteamVR, it starts, and room setting can be launched.
However, only gray empty screen shows in Vive.
The warning to “enable direct mode” repeatedly pops up, but when I click enable, the SteamVR NEVER restarts properly. (It closes, and stop there forever.)

My system setting is below.
OS X High Sierra
NVIDIA GTX980
Web driver and Cuda installed.
HTC VIve connected to HDMI port.