Service worker based offline page not working

So I had asked a question few days ago about offline functionality and I got the answer of using service worker to cache my resources for offline.

Which I did and it works perfectly fine in browsers but when on the app it shows me webpage not available WebView notice.

What should I do to make it work? I have disabled the offline page in the interface panel. Am I not supposed to do so? And is it that which is causing this error?