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.

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
Web driver and Cuda installed.
HTC VIve connected to HDMI port.