gulp unknown command

1. Change order of items in "Location of external tools": in the Visual Studio > Tools > Options > Projects and Solutions > Web Package Management > External Web Tools

 PATH, node_modules, Web/Externa\ DevEnvDir \DevEnvDir

2. Ctrl + S in (I think) gulpfile.js or nuget.config) to download gulp modules

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If gulp is still unrecognize uninstall node and gulp. Install again. Some people claim they needed to add an env variable but I didn't have to.

1. uninstall -g gulp
2. Windows uninstall program - uninstall node js.
3. Google 'install nodejs'. Download .msi file, run install. It installs gulp by default I believe.
4. Restart Command Prompt