To install node v9.0.0, use

nvm install 9.0.0

Then check the version

node -v

It should be v9.0.0

If there is a version mismatch, use

nvm use 9.0.0

The output should be Now using node v9.0.0 (npm v5.5.1)

Made sure, you have already installed the nvm

You can also check the Documentation for details.

Likely it means you are behind a proxy server.

To tell nvm about it you need to run the command:

nvm proxy [url of your proxy server]

For example

nvm proxy http://example.com:8080

For docs on that command and other nvm for windows commands see https://github.com/coreybutler/nvm-windows#usage

nvm install 8.10.0 is for installing proposed node version locally.

In order to use it:

nvm use 8.10.0

Note that you need to run this command as administrator.

You can always set default Node.js version:

nvm alias default 8.10.0