Request failed "404 Not Found" when installing packages

Question

NB: Adding this Q&A because none of the Q&As related to Request failed "404 Not Found" mention what solved the error for me.

Running yarn install or npm install results in the following error: screenshot of command line

Tried this and similar resolutions: Installing package npm fails with 404

Answer 1

In my case the problem was that I was trying to install a private NPM package without being logged in to NPM.

To resolve:

Run npm login and follow the prompts.