Boss Machine - local server previously worked fine, now won't load!

Hi all - this is my first post on the forums, hope to get some assistance if possible!

I am working on the Boss Machine express.js routing project. I was able to preview it locally on the required port (4001) without issues…

… then I royally screwed it, and decided it’d be cleaner and more straightforward to start over. I deleted all references to the project from the filesystem, including from the trash. I then downloaded the source files again and started over.

However, now the project won’t load on Chrome via http://localhost:4001/ - I have been able to preview locally via VS code, but now whenever I run the project’s test suite it runs incredibly slowly (i.e. 1m to run the entire test suite - previously it would run in something like 270ms).

I have tried deleting the browser’s cache and a couple of other tricks but to no avail. Wondering if anyone has any clues please?