Updated test in Cypress does not run automatically

I've just started investigating Cypress, and I seem to be unable to get the most basic functionality of it to work.

Essentially when I save a test file, the documentation implies that the browser should re-run the updated file and present the results immediately. Yes, only Step 2 of the Tutorial. For me, the browser (chrome) does absolutely nothing.

The changes only seem to be reflected when I close and re-open the application, which isn't a practical solution every time I make an update to a file.

I note that there are suggestions to do something with IntelliJ/Webstorm Safe Save, but I'm editing the file in Notepad++, so have no idea where that configuration would need to happen, if it's even relevant. (plus i think that's a different issue). Also have the problem in Visual Studio 2018, Windows Notepad, and Textpad

I'm on Windows 10, running the Direct Download version, via the application GUI (so not using the CLI at all).

What am I missing?