For mine, this is the only way it would work:
VivePort says I already have VIVE & SteamVR installed, which I know I have SteamVR installed but I wasn't sure about VIVE...unless that happens as you start the VivePort install?
It also says I can skip this step but offers no skip button so I can only click install.
Steam was already open but SteamVR was not - I was logged into Steam.
I started the VivePort install, it got to the part where a Steam pop-up appeared - looked to be logging me in...again?
Then, it got to the endless "Installing Steam..." part. I right clicked on the Steam tray icon and clicked on the bottom SteamVR link.
This started a chain reaction of installs and now everything works a little closer to how it probably was meant to - headset and all.
Good luck!
