Error: Node Sass does not yet support your current environment: Windows 64-bit with Unsupported runtime (57)

[MarkMasiak]

If you are seeing the error: "Node Sass does not yet support your current environment: Windows 64-bit with Unsupported runtime (57)"

Update node-sass to v4.5 or downgrade node to v6. There was never support for Node 8 in anything but release 4.5.3

Node 8 should be LTS Version

this is due to the build in the SharePoint Client Side pre-requisites and the issues with Node Version and Node-Sass compatibility - trying to figure this out took a while. Basically the following versions install by default which are not compatible:
Node version: v8.9.4
Node-sass version: 3.13.1

There's also an issue with Node-sass with having different versions in different locations so you need to check your install path "C:\Program Files\nodejs" and "C:\Windows\System32"

compatibility version information can be found here https://github.com/sass/node-sass/releases

I got the solution to work by upgrading
Node version 8.9.4
Npm 5.71
Node-sass 4.7.2
Libsas 3.5.0

some commands to check versions
node -p "require('node-sass').info"
npm ls node-sass

check to see if updates required
Npm outdated
Npm update

Npm install node-sass