It seems to only work in Chrome. Firefox mobile shows nothing unusual.

Works fine on firefox desktop for me. Its some kind of locale issue I think, as others have suggested.

It appears/functions on iOS Safari just fine.

Firefox on android has a checkbox in the menu for Request desktop site. Then it loads the spinner.

I had to request the desktop site on firefox mobile to be able to see it...

Once the spinner picks the right number, a code is revealed.

Nor does firefox on desktop. Chromium did work though.

Safari 10.0 works fine as well.

Add &hl=en to the URL and it should work.

This makes it work for me also. Mods should edit OP URL to include this.

They did but now they took the "spinner" part out of the url

Edit: Nevermind, already fixed

Same here. I suspect because google insists to redirect to my non-US country?

Not sure where you're located, but in Google Canada I see the spinner.

I couldn't see it in the French version of google.ca, but when I opened the English version in a private window it worked.

It solely seems to depend on the Google user language settings. Works for both the Canadian and German Google with the language set to "English". One gets what one would expect (with "spinner" roughly translating to "idiot") when trying this with the German Google set to German.

Was redirected to .co.in and spinner works.

It looks like this: http://streamable.com/orob8

It displays a graphical spinner (think a wheel from a game show or something) and spins to a random number on it.