It keeps installing, and asking to restart, then repeats. I’ve tried both VS Code and Atom.
It was fine before I updated the OS 
Figured it out. After checking the dev tools > console, for some reason the platformio binary somehow cannot be installed via pip. $ platformio --version will always return unknown command.
The solution: I uninstalled via pip $ sudo pip3 uninstall platformio. Then reinstall via homebrew, $ brew install platformio. Restart vscode. All good now.
I recommend to brew uninstall platformio and use our portable installer GitHub - platformio/platformio-core-installer: PlatformIO Core Installer