Progressive Web App - Service Worker not serving start_URL

Just a note... you notice above that the pages are being served over "https." But, if you have everything else right, and are not using https, you will get this same error message.

Noted from Register A service worker,

If we register the service worker file at /example/sw.js, then the service worker would only see fetch events for pages whose URL starts with /example/ (i.e. /example/page1/, /example/page2/).

Inline with the shown error and given in this documentation, check the following:

1. Define a start_url property in your manifest.json file.
2. Ensure that your service worker properly caches a resource that matches the value of start_url.

Also, check this tutorial and see if it will help you.