Browser doesn't show favicon.ico, but it exists

Browser will load from cached data. Try updating your call to force an update via. new file-name.

<link rel="shortcut icon" href="/favicon.ico?v=2" type="image/x-icon">

I see it used as icon when I browse to your page.

If you have visited your page before (duh!) it's likely because the browsers remember that there wasn't any icon there before, and don't update it right away. Browsers remember the icons for different sites, so that they don't have to request it every time that the site name is shown (for example in the bookmarks or the history).

Also, it's not guaranteed that every user sees the favicon, some browsers simply doesn't display some icons sometimes, for no apparent reason.

Takeaway from the Rest of the Similar Posts

It is Important to Close ALL the Windows for the Browser You Are Testing against and Start It Fresh to See the Change Happen. (Doesn't Work on Edge)

Aside Notes

I have stumbled upon this issue myself. After researching other answers, there are many suggestions to fix it.

Some people can't rid of the old icon: How to clear the icon cache of Chromium browser

Others wanted to force refresh: How do I force a favicon refresh